1982 xj750j maxim starting issue

I bought this bike last fall as a project so I could start riding again. This is my first Yamaha so I am not very familiar with them. I downloaded the repair manual and it covers everything except the starter clutch, so it hasn't been much help.

i picked this bike up for $600 after tax and title, being told it only had one little problem.... It ran and drove when i picked it up and the previous owner claimed he rode it every day, weather permitting. the only thing i really noticed wrong with it was when it was on the kickstand it would spit up a little oil but he had removed the filter box and was using cone air filters so he had just tie the hose to the frame, right along the kickstand. the other problem was that when i hit the starter it would spin freely for a few seconds then catch and start right up. i took the bike home and started tearing into it. the wiring harness was a cobbed up mess of melted and taped wires, the carbs were from a 70's model Honda and had tape wrapped around them to fit the intake boots with hose clamps holding them on, amongst other issues. i ran a new wiring harness, eliminating ALL of the starter safety features (neutral sensor, kickstand sensor, etc), picked up the right carbs and rebuilt them with oem rebuild kit and a 6 sigma jet kit, fabbed up an oil overflow reservoir from square tubing and a chevy valve cover breather, and replaced the aftermarket hand controls with the original hand controls. the bike sat for roughly 4 months without being started. when i went to start it up it would spin freely until the battery was dead. i replaced the battery, replaced the solenoid, rebuilt the starter, and tried to start it again. it spins a lot faster now but still takes a few seconds to engage the starter clutch. i was told that the springs in the one way clutch get weak and gummed up and that its a common issue with this model so i ordered new springs. the local Yamaha shop told me the starter clutch was right behind the clutch, but it isn't, i found that out today when i put in a new clutch kit. the bike will start, run, and drive but it takes a good ten seconds to engage the starter clutch, if the bike is warm it seems like it starts up much easier. if its cold sometimes i have to hook up a jumper pack to get it started.

so before i do anything else i am wondering if i can get to the starter clutch assembly through the left side covers or do i have to split the case? or any other suggestions on what to do? i contemplated running an engine cleaner through it in an attempt to get the possible gunk out of the starter clutch but im afraid that if there is sludge build up it will clog the oil pump.

 

You do have to split the cases to get to the starter clutch, but their are a few things to try first.

Do you know what kind of oil is in the engine now? Try doing an oil change and be sure to use regular motorcycle specific oil. Automotive oils tend to make the starter clutch and transmission clutch slip. I use standard Valvoline 20-50 motorcycle oil, but it is fairly expensive. Other members have been reporting no issues with Shell Rotella 15-40, it's primarily a Diesel engine oil but it meets all the requirements for motorcycles and costs considerably less.

If that doesn't work you can try removing the starter motor and spray the starter clutch down with a good carburetor cleaner to try and remove any built up gunk. Followed by a couple of oil changes to flush the carb cleaner out of the crankcase.

 

Welcome to the club. Sounds like you've got a few things to get sorted. The constant velocity carbs on these bikes are difficult to dial in with the pod filters unless you are really knowledgeable in that area (I'm not). It also sounds like you're familiar with old bike resto and many of the things needed to make one truly road worthy. Have you checked the valve clearances? Have you compression tested the cylinders? How many miles are on it? Imo if all else fails rebuild your bike to stock. There are plenty of 750 maxim parts available.

Gary H.

 

I don't know what was in it but it was black and way over filled. No chunks were in it though so that's one good thing I guess. The book (obviously) says to use yamalube or whatever it's called or a non synthetic, non additive, oil of equal weight. Wal-Mart carries a cheap oil that meets those qualifications but I can't remember the name so that's what I used. I soaked the clutch kit in new oil as suggested by the manufacturer before installing. The clutch grabs really well, it was a" high performance clutch kit" and it blows the old clutch away. The carbs are really close to being dead on, cylinder one is running slightly lean as compared to the other 3 (using an infrared thermometer the pipe on cylinder 1 is about 5 degrees different but the other 3 are all running the same temp).
I am really, really not wanting to tear down the block and split the case. I haven't measured any internal parts but it runs smooth and doesn't backfire or misfire so I'm going to assume everything is still decent. I have not done a compression test either but from push starting it I still think it's pretty decent. Unfortunately mileage is unknown, it has forks from a 40's model bike (I think the triumph that was used in ww2), risers, drag bars, drum brakes, and no gauges. It's titled as a 75 Honda cb750 with about 1500 miles but who knows how accurate that is.
I've heard of people running seafoam in older car engines to clean them out, followed by an oil change after about 15 minutes of running. Is that safe to do in bike engines or do you think it would be safer to stick to carb cleaner? The only problem I've seen with the seafoam is breaking loose sludge and clogging the oil pump, which is a good way to burn up an engine in a short amount of time.

 

Read the first link in my signature.
Then read the second one.
Then you can start working on the bike in earnest.

You can use Seafoam in the crankcase. The oil pan is well baffled, so there is little risk of a big hunk of sludge breaking loose and blocking the oil pickup screen.

I'd spray the starter clutch down (as BigT described) during the oil change, then run it up to temperature with a cheap non detergent oil (easy to find at a farm store) to flush the remains of the oil oil out (the non-detergent oil will have an SB rating, so it will not have any friction modifiers (or any other additives). Then follow up with an oil and filter change with a JASO MA rated oil.

If the starter clutch continues to slip after that you will either be splitting the cases, or becoming an expert in bump-starting.

Of note is the fact that once the engine is out of the frame you do not have to tear down the top end in order to remove the lower case. This will save you quite a bit of time, a lot of money (gaskets), and eliminate the risk of damaging the piston rings.

Another thing to note is that the alternator chain guide is known to fail due to age. This is kind of a big deal, so if your starter clutch is in need of rebuilding then you should view that as an opportunity to take care of two problems at once.

 

I will check into those links after work tomorrow. I haven't checked yet but are the oil pans on these able to be removed while the engine is still in the frame? I was thinking that I'd do both seafoam and carb cleaner spray down then change the oil and drop the pan to make sure there aren't any metal shavings or debris hanging out in there, gaskets aren't too expensive anyway. The only Yamaha shop nearby is about 20 miles away and we had a disagreement on my last visit so I'll probably just order a couple more filters online unless Napa has or can get some in.
My other question is since I already plan on removing the oil pan is there an oil drain hole under the starter clutch like there is on the clutch side? If so I may be able to get in with carb cleaner better that way.

 

The oil pan can be removed with the engine in the frame, but you will have to drop the exhaust, and do some funku manouvering ot get all of the machine screws out.

There is a oil drain below the middle gear. Generally we recommend not toucing it since they can snap off if they have never been removed (most will not have been). It also dosne't lead to the starter clutch, so there is no reason to remove it for this job.

The only other oil drain hole is next to the oil filter housing, so I don't know what drain next to the clutch you could be talking about (as there isn't one).

The best access to the starter clutch is by pulling the starter. You could pull the alternator rotor, stator, and alternator shaft bearing, but that is a ton of work for very little reward given what you will be doing.

 

I meant inside the case. I noticed when I was changing the clutch out there was a curved piece of metal in the bottom back side, similar to the crank scrape in a car's oil pan, when I pulled it out there was a hole under it leading to the oil pan. I already have the exhaust off so that's not an issue. I meant taking the oil pan off, jacking the bike up, and trying to spray the starter clutch from the bottom if the case had a similar hole

 

I elaborated on that when I said that the best access is through the starter hole. You get marginally better access with the oil pan off, but portions of the lower case will be in the way and in my opinion is is not worth the effort for only gaining slightly better access considering that you will be flooding the starter clutch with solvent when you spray it down. You certainly are free to do it that way and you may end up making the better choice by doing so; it just isn't how I would do that job.

 

Yea I see what you are saying, I looked at it today and it's definitely tight trying to get the pan out.
I guess one detail I forgot to mention is that my oil drain plug is stuck. When I drained the old oil I did it from the clutch cover because I was afraid of snapping the main drain plug bolt (19mm i think it was). I tried it with a ratchet first and couldn't get a good grip so I tried an 18" breaker bar and still couldn't get it loose. I tried putting pressure on the bar and tapping with a small 7oz hammer but even that didn't work. Unfortunately I've seem people locktite or epoxy drain plugs after they screw up the threads and I'm wondering if that's what the previous owner did now. So if I break it off I have to drop the pan anyway and I'd rather get that sorted out before I put solvent into the engine.
If I can get it loose I'll just take the mentioned advice and spray through the starter hole. If I have to drop the pan I'll spray from the bottom then through the top. Once I get it started back up I'm going to add seafoam while it's running and let it cycles for 10 minutes or so then I'll do a flush and final oil change. Even if it doesn't fix the starter clutch it should help clean the oil return holes in the head. If I can get the starter clutch back to engaging after a couple seconds I'll be happy enough for the remainder of the summer, if it ever quits raining. Save the tear down for those boring winter months.
Thanks for all the help and advice though, hopefully it helps out on this part.

 

Used oil pans are cheap. I wouldn't futz with the stuck drain plug.

 

Been spraying pb blaster on the oil pan drain bolt for a couple days, put a wrench on it tonight and it broke loose so easy I about fell on my face. Oil filters came in today too so I'm ready to try spraying down the starter clutch. Probably won't get to it til Saturday night or Sunday, trans am blew a brake line so I'm dealing with that first. I'll let you know if the carb cleaner and fresh oil help on the bike though. I appreciate all the input

 

Added fresh oil and seafoam after spraying down the starter clutch. The bike will start without a charger now but I can't get it to idle below 3000 rpm. When I had the aftermarket grips on I couldn't get it to idle above 600 rpm. I thought putting the original controls back on would fix the problem. Any suggestions on a fix? I'm debating on trimming down the wire casing so it gives me more cable to play with

 

Please elaborate on trimming down the wire casing. Hanging idle is usually caused by air leaks around the carburetor. You can use an unlit propane torch to test for air leaks. I assume you tried adjusting the idle with the large idle knob in front of the carbs.

 

Unhook the throttle cable at the carbs and see if you still have a hanging idle. Don't take acton without diagnosis. You can't just trim the casing. its length is an integral part of the cable functioning properly.

 

Big t I put brand new intake boots on when I rebuilt the carbs. Depending on which twist grip I put on depends on if it idles high or low but neither of them stick. I played around with it for awhile trying to adjust the idle knob, with the factory grip I can let the idle knob out all the way but the cable isn't long enough for it to drop under 2800 rpm. With an aftermarket grip there's so much slack in the cable I can turn the idle knob up all the way and adjust the cable out all the way and there's still so much slack it only goes up to maybe 700 rpm. After looking at the grips I noticed the difference is the plastic around the cable. The original has way more plastic so it can't roll back far enough to give me the slack I need, the aftermarket grip barely has any plastic so it rolls back too far. I'm thinking that I can use my dremel to remove a little plastic on the original grip so I can get more slack in the cable, if I take too much off I'll still be able to use the cable adjuster to take up the slack. I had the bike running for about 15 minutes using the aftermarket grip, I just had to hold it a little to keep it up around 900rpm. The repair manual says the idle should be around 1000 but that seems too high to me. The idle was a lot lower before I put that 6 sigma jet kit, new air filters, and straight pipes. I didn't think it would make that big of a difference

 

Big t, when I mentioned trimming the casing I meant using a dremel to cut a couple wraps off to allow more cable to be exposed. I've done it on four wheelers and dirt bikes before, you have to use a small bit to remove the burrs though otherwise the cable can get caught and stick or will wear out and fray easily. It's not the right thing to do but once you get it trimmed to a working length you can measure it and buy a new cable that is the same length.

 

I'm thinking you need a set of cables that is the correct length for whichever throttle tube you choose to use.

Your idle should be 1100 RPM give or take 100. Any lower and the primary chain will begin to slap into a very expensive oil nozzle and eventually cut it in two. Any higher and you're just wasting gas and making the engine run hotter at idle than is good for it (over the long term).

Now that you explain your cable cutting I agree that it is not a bad idea.

I still would like you to unhook the cable from the carb and see if you can set the idle to 1100 RPM and have it stay there. That will isolate the issue to the cable, or tell us that there is some other issue.

 

I unhooked the cable at the handle because it's a pain in the butt to disconnect at the carb. It allows enough slack for the the throttle to sit on the idle adjuster screw all through adjustment. I have the same problem as when using the aftermarket throttle though, I can turn the knob in as far as it will go by hand and can still only get the idle up around 700. I'm not sure if my knob is actually bottomed out or if it just needs a little help from a wrench to get over a dirty thread.

I really just want the original throttle back on, that's why I mentioned trimming the plastic to get the idle down. I paid $20 for the assembled hand control with throttle cable, so if I mess the throttle up I'd just have to get back on eBay and buy a used throttle

 

I think you had better pull your tank and have a good look at the idle adjustment screw then. Something ain't right.

 

I don't have a stock tank on, I have a coffin tank so it allows a pretty clear view to most of the area. I will agree that something isn't right with the knob though. It has about 1/2" of the shaft shiny from being adjusted so much. So you'd think that it would move the throttle the same distance since it's basically just a threaded rod but it doesn't. I disconnected the cable at the handlebars so it would have several inches of slack then turned the idle out about half inch. The throttle had clearly stopped moving well before that so I reached in and tried to push it back gently but it wouldn't go so I assumed that was the stopping point (idle around 500 at that setting). I watched the throttle as I turned the adjuster knob in, as far as it would go easily it only took the idle up to 700 and barely moved. In my experience with off-road bikes you should have way more range than that and the knob should noticeably move the throttle the entire time, not just the last couple turns. Either way if I use the stock grip I need a longer cable or to trim the plastic. If I use an aftermarket grip I'll either have to fix the adjustment screw issue or get a shorter cable or adjustable grip. I'm taking Friday off work so I guess I'm pulling the carbs for a closer inspection. Fixing the knob won't help with the stock grip either way though. I currently have 2 oem throttle cables, one has frayed strands that hang up really bad and the other I broke the adjuster on while messing with it today. Don't really want to spend $18 on another if it's not the right length for either grip I have

 

Got the factory handlebar controls wired up this morning and started messing with the carbs. I think the previous owner put a different spring on the idle control knob because it was so long the knob would stop almost immediately after touching the plate. I pulled the spring off and trimmed it a little bit before reinstalling. I also used a soldering iron to weld the plastic throttle cable adjuster back together. Now I'm just trying to dial in the idle. On the first start it was up around 2700 rpm so I shut it off to adjust. Started it back up and had it down to 2200 rpm but forgot to turn the gas back on.I think I'll have it dialed in before too long then maybe I can get a road test in, or at least a driveway test.

 

WHat does she idle at with the idle control knob uninstalled? If it still idles high then there is an issue not related to either the throttle cable or the idle control knob. With the idle control knob backed all the way out the throttle plates should be fully closed.

 

I went back to the aftermarket throttle that was idling at 500 with throttle knob all the way out. Got it set to 1100 then put the air filters back on and it dropped down to roughly 900 so I adjusted a little more. I was having problems with it wanting to spit, sputter, and hesitate when revving and realized carb 1 is flooding. Kinda pissed because I've already taken the bike to the shop 3 Times to have the float adjusted and every time it's come back exactly the same. They swear they adjusted it but upon inspection they never even took the carbs off, called to complain and they told me to bring it back for adjustment free of charge. I think I'll just do it myself this time.

 

And every other time. You are the best carb tech there is (once you learn how).

 

Between working 60 hour weeks and getting griped at for the garage smelling like gas I thought it would be easier to take it to a Yamaha shop. Guess I was wrong. I'm taking the bike to a buddy's house next weekend to finish the carb work up, family stuff with the woman trumped the bike this weekend.

 

That's why I had to find a house with a single car attached, and a double car detached garage.

 

Carb cleaner cleans of the gas smell; Simple Green cleans off the carb cleaner smell; nitrile gloves prevent your hands from getting smelly in the first place.

 

See, you're learning already--- how many times have we posted in various forums...... DON'T TAKE YOUR BIKE TO A DEALER FOR REPAIR

1. The majority of them don't know how to work on a bike this old--- ya can't hook a computer up to it and have it tell you what to fix

2. The majority of them DONT WANT to work on a bike this old

3. Will charge ridiculous $ to either get you to not have them do the work,?or make it more worth their whole to TRY to do the work ( which will be minimal at best)

You want carbs done right? Either send them to me, or some someone like me, who knows how to rebuild them and set them back up to factory basic specs..... Or take the time to learn how to do it yourself. It will take time and $ either way, but you also know it will get done correctly.

See my forum from yesterday called Beautiful Carbs to see a couple racks that are being sent back to their owners tomorrow for an idea of what I do. Each rack gets a total disassembly, each part cleaned and evaluated, any questionable parts are replaced with new parts from Len ( unless someone already purchased other parts --- not really encouraged because I can't guarantee correctness then), idle mixes set to preliminary setting, floats set to preliminary setting, rack is bench synced and sent back ready for you to do your wet-setting, running sync, and colortune.

If you want more details, contact me privately.

Dave F

 

i try to never assume anything~ it can be problematic

 

This is where I'm out now:
I'm at my buddy's house with the bowls opened. The carb that was flooding has a hole in the float that I didn't notice before, there was water in all 4 Carbs (the shop left my bike outside, I wasn't happy), and the spring on the float needle was sticking out so it couldn't close. We got the spring tightened back up but I can't find anywhere to buy new floats. I've checked Amazon, eBay, and bike bandit. So my next question is, where do I acquire new floats and what's the price?
I also drained the gas tank, put in fresh gas, and changed fuel filters.

 

Start a conversation with user Chacal. The link to his catalog is prominantly displayed in the upper right corner of every page of this forum.

Even being left in the rain you should not have any water in the carbs unless there is a host of other problems that need to be addressed.

 

Someone should have a good used float here somewhere. I don't think you could buy one from Yamaha anymore unless xj4ever has one. Is the hole in your float just a blemish and could you fill it with some JB Weld to get you by for awhile?

 

Kmoe it's possible there was water left in the tank from when I had a new petcock welded on but when I took the bike to the shop I left the air filters off to save them time. So it sat outside in the rain for a week while they had it. The gas that was in the carbs had turned to gel and the only time I've seen that happen is when it gets mixed with water. We tore the carbs apart and cleaned everything out and then drained the tank and blew compressed air through it until there was no more fluid coming out and let it sit in the sun for a couple hours, it's black so it got pretty warm. I filled the tank up halfway and put the lid on then turned it every which way and it's not leaking anywhere so if the water didn't get in from rain it might have been in the gas can I used previously. I will check with chacal for a float after I call the bike salvage yard in the morning.

Mn maxims, the hole appears to be on the molding seam, it may have been a thin spot that just wore through from the plastic aging. I'd try to plastic weld it before I used j b weld but I'd rather find a replacement before I try any MacGyver techniques. I know hogfiddles mentioned he rebuilds carbs but I'm on a pretty tight budget so while I'm trying to save money there are a couple corners I'm not ready to cut yet

 

those floats aren't hollow, more like a foam and don't fill up with gas. take a container of gas and put the floats in it, see if that one floats any different than the others. you have to adjust the floats anyway so small differences can be adjusted out.

 

Plus one with Polock says. See if it floats in gas any different and wet set your carbs.
If you are on a budget then it won't hurt to try.
Sounds like the shop you had the bike at should have at least covered your bike if they knew the carbs were exposed to the weather.

 

One would think.

Gary H.

 

Yea I talked to a few guys who are more familiar with the shop and they all said they drive to Somerset or Lexington to get work done because they don't trust those guys to do more than putting tires on the rim. So I'm done with them and will not be giving good reviews to anyone that asks. I tried the salvage yard but they wanted me to buy used carbs for about $100 instead of individual parts. I checked eBay for mikuni floats and they are around $35 each, chacal said he could ship me a guaranteed good used float for around $25.

Polock, that is a good idea and I hadn't thought of it. I was thinking about switching that float to a different bowl to rule it out before spending money. I already tried switching the float needles out but 1 is still the only carb leaking. My buddy did try to adjust the float but after 5 tries with no results we moved onto different things.

 

Alright it's been almost a month now and I thought I'd update. I took the carbs back off the bike and took all the new parts out, separating them into bags so they'd go back into the same carb. I found little tiny flakes of rust in the carbs so I removed the float valves and sprayed carb cleaner through the fuel line, I think the rust got in when I initially tested them without a fuel filter. Bought new valves with screens and matching needles. Put each float in a cup of gas and they all float the same. I did notice that both 1 and 3 had a bent hangar so the floats weren't level, fixed that. After 4 bench tests I got all the carbs set to where they aren't over flowing. Mounted the carbs and started the bike but did not hook up the throttle. Bike started much quicker and held a steady idle until I sat down then every time I moved it would idle up. Sprayed carb cleaner on the intake boots and discovered 1 didn't have the vacuum cap on all the way. Pushed it down and adjusted the position of the little spring clamp that holds it on. With the bike running I stood beside it and leaned it side to side to simulate hard turns and none of the carbs are leaking that way either. Everything seems to be working fine so I guess the next step is to have a more reliable shop sync the carbs properly. I want to thank everyone that provided input on this. On another note a friend gave me a 1994? Kawasaki ninja 500 last weekend. Needs a new flywheel ($300), petcock ($75), and carb work (of course). On the bright side it has new tires, chain, sprocket, plugs, and underglow. She laid it down (assuming that's what caused the flywheel magnet to break) and is too afraid to ride anymore and doesn't want to fix it. So I guess my next project is lined up already

 

You can do this.

Gary H.