1982 yamaha maxim question

I just recently bought an 82` maxim 750. I went for a trip about 20~30 miles today and noticed a couple of things. First I noticed that after the bike warmed up it was a little bit louder everytime I shifted gears. Not sure why but it appears to be temp related.It does not strugle going into gear but it was louder.
The second thing was that after it warmed up there was some smoke coming from the tube out of the crankcase. This looks like some sort of vent tube but it is open on the end, There is nothing connected. The idle also seemed to go up when it warmed up. When I start it in the morning with no choke it idles at about 1500rpm and then when it gets up to temp it idles at about 1100rpm. Today on my trip when I was at a lite it was at about 2500rpm.
Thnaks for any help
Joe

 

I opened up the oil plug and it has a slight smell of gas. Could this be blow by? The guy who I got it from did a complete re-build including sync of carbs. I might try to do an oil change and see if it gets any better. I assume that the round twist nut on the center of the carb rail is the idle adjust? Also it seems to be running rich but I guess for an air cooled engine thats better then lean.

 

Check the Fuel Outlet at the Petcock to see if the Petcock is "Leaking-by" any Fuel.

Leaking-by is a problem that can cause the Crankcase to be contaminated with Fuel.

Real cheap Insurance:
Add a Briggs & Stratton Inline Fuel Shut-off Valve: $10.00

Color the Hose Clamps and extraneous Red of the Valve with Black Nail Polish.
Makes the Mod virtually disappear.

 

My friend you have much reading to do. If there is gas in the oil, then the float needle is not doing it job. Never trust what the PO tells you. There are some really good how too's in this forum on carb cleaning and balancing. Don't start adjusting things untill you are sure that you know what you are doing. All the info you need is here, and plenty of guys willing to help. Step back and take a deep breath, you are in for a long ride. And if you are patient, when you are done, you can go for a long ride

 

How do you know when a PO is lying?

His lips are moving.

 

i think the P.O did a good job on the rebuild. The bike fires right up and seems to run fairly strong. Not bad for a $500 bike. My last bike was a Ninja 600r so this a bit different. What I can say is that when I go to start the bike in the morning It does not seem to need the choke, It starts right up and takes about 2 minutes or so to smooth out. I can smell that it runs rich but I dont think I want to mess with carb jetting yet. Would you do a oil change to see if prior to him rebuilding the carbs oil may have leaked into the oil. I dont think he did an oil change. The level is right but the oil looks real dirty.What weight oil should I use.

 

pic of bike

 

I notice that the petcock has 3 positions ( pri,res,and on). Mine is set to pri is that the correct position. My Ninja was F.I and only had on and reserve. Maybe thats my problem.

 

Should not be left on "PRI".

The fuel cock is vacuum operated and will only allow fuel flow in the "ON" and "RES" positions if there is engine vacuum. This protects from leak float needles adding gasoline to the oil, floor etc. "PRI" stands for prime and is to be used to fill dry carburetors (after a cleaning for instance).

 

Yeah I just thought that pri was primary and not prime but I thought wrong. Should I do an oil change because I may have flooded the engine.

 

You would change your oil immediately.....wont hurt.......petcock should be in the "On" position.......definirtly not "PRI" position......

Try those changes & go for a ride.....

The '82 XJ750J is a great, fun, & a powerful bike.......have fun with it....

Grab yourself a factory workshop manual.....it will pay for itself the first time you use it....

 

You may luck out with just an oil change, I know that when I flooded my case it ran like crap. 2 think you should think about getting though are an inline fuel filter, and an inline fuel shutoff valve. Your tank only has a screen in it and still lets the smaller bits of crud thru causing more frequent carb cleaning. And the inline shut off is more for peace of mind.

 

Thanks guys. The good news is that I have only put on about 100 miles. Hopefully I did not dump too much gas in the crank. The P.O did a complete carb rebuild so if it is set up correct then I might luck out. The bad news is that I ran for 100 miles like this LOL. Anyway I called my local dealer and they have an oil filter in stock for $10 but what weight oil should I use. The parts dept said 10~50 does that sound right. Can I use regular motor oil off the shelf at Walmart or do I need some special oil. I know that I will not use synthetic. Thanks for the help.

 

Synthetic is not the issue, you need to use an oil that does not contain friction modifiers. You will pay more from the dealer for oil, but they should set you up with something that will work with wet clutches.

Everybody has their opinion on oil, mostly because it is difficult to actually tell which oil has friction modifiers that will affect the clutch. Search for oil advice in the forum and you will get ALOT of results. As for weight, the maunal says 20W-40 (10W-30 for LOW temp riding) - which is hard to find but many people work with different weights. I use 15W40 shell rotella - due to recommendations on this forum and what I have read about diesel oil standards.

 

O.K this might be a problem but I`m not sure. I do not have a stock air filter and I actualy have 4 individual pods ( 1 on each carb). I think this means that I dont have a vacuum connect to the petcock. There are 2 connections there but 1 is blocked. When I put the switch to on it runs for a few seconds and then stalls. If I prime it then it runs a bit longer. Also there are 2 lines coming off of the crankcase and they are both open and not connecting to anything. My guess is thta these would connect to the stock air filter. They are 2 different diameter hoses if that helps. On second thought would the smaller diameter hose be the vacuum to the petcock? Well I attached a pic so any help would be great. Like I said the only way the bike will run is if I set the switch to "PRI" or somewhere between "PRI and ON".

 

The big hose by the starter should connect to the front of the airbox. That being said, since you have pods, the vent will be useless. But, hook it up anyway to at least catch oil spray.

On each of the carb boots, there should be a brass nipple covered with a cap with a clamp, all except one. That one should have a small tube coming off of it to go to the small nipple on the petCOCK. (Funny... I don't have any problems typing that on MY keyboard.....). With that disconnected, the petcock has no vacuum pulse with which to operate.

The petCOCK (oops, gotta fix the caps button) should be set to ON for normal running, RES as you approach empty and the bike tells you it needs you to switch to that, and PRI for when you ignored the RES too long and have run out of fuel. The ON and RES settings are vacuum operated by the small tube that you hooked up from the intake boot. The PRI is passive gravity feed and will run whether the bike is running or not.

If it smells like there's gas in the oil, then there is. Change it. Keep tabs on that for a bit. You may just have some residual leakdown and not have to do much with the petcock. Easiest way to check......put the petcock to ON and pull off the larger fuel line. See if any fuel runs or keeps dripping after a minute. A couple drops may come down, since there was fuel in the line, but after that, you shouldn't have ANY coming through. If it does keep coming, time for a rebuild there, or shut-off switch.

If you have pods, you'll also want to find out if the jets have been replaced with the appropriate ones.


You also said that it seems to run rich, and that you don't need to use the choke. Could be that some of the jets are plugged and you're only running on choke. DO a plug chop and let us know what they look like. Also, when you're running and warmed up, what happens as you slowly pull the choke lever (and play with the throttle a bit.....can you bring the idle up by using the choke or does it only kill it? some choke should bring up the rpms, but if it just kills it you may need to do some carb work.

Welcome to the forum. This is a GREAT group and you'll have a wonderful time here. Nice ride, man!!

 

First what is a "plug chop". The choke seems to work fine because the rpm`s do change when I move the lever--It does not stall but the rpm`s go up like one would expect. The P.O did a rebuild and I trust his work because he does lots of builds. I guess the first thing would be to connect the vacuum line then see what happens. There is a small glass fuel filter and when I put it to run I can see that no gas is geting into the filter. It`s not a directional filter so thats not a problem plus like I said when I put it to pri it flows fine. If I run it on pri will it flood the engine if the carbs floats are set right? Anyway I`ll check to see if I can hook up the vacuum.
Thanks for the compliment on the bike.

 

I assume this is what your talking about for the vacuum (see picture).Does it matter which carb port I hook up too? The one I took the picture of is the easiest to get too. Damn I need this to work so I can make it to laconia with a bike this year instead of driving my "Z".
What is the second air line coming out of the crank case smaller diameter hose?

 

the little line you can use for the petcock there shouldnt be any line going to the crank case from the petcock. the smoke coming from the breather hose can be 1 of 2 things blow by or condensation did you wash the bike before you noticed it or if just rebuilt it it could be the rings havnt seated yet. you need to change the oil for sure and make sure your not getting anymore gas in it. if he had the line to the petcock off it probbibly has a bad petcock. the breather tube you need to get a filter on it if your getting alout of smoke out of it add a peice of hose that resists oil (fuel hose will be ok) run it up hi so the oil wont come out and hit the tire plus alout of the oil will run back down into the engine. another reason for the smoke coming out is it overfull of oil?
if you are running rich with pods they either jetted it to rich or floats are wrong height or leaking by even if the petcock is working good if you have a bad float all the gas in the line will run past the carb and into the engine. pull the plugs see wich one is black if they all are probbibly jetted rich or he set all the floats to high. if you pull the carbs get the jet numbers see if they are stock i have herd of people getting them mixed up not sure if you can on those carbs

 

I changed the oil and filter a few minutes ago. It took 3 quarts and I hope that sounds right.So are you saying that I can hook the petcock to the carb I am showing in the picture above? I think the petcock is working o.k and he probably just bypassed it.

 

just make sure if your going to run it that way to turn it to the on posisition and make sure no gas is coming out i would definately put an inline shut off valve in it especially if your floats are high it will put gas back in your crankcase and if you dont catch it the motor will be history

 

I hooked up a line and now it works in the on position. My idle is at about 1200 rpm or so and seems to run pretty good there (not sure if thats o.k or not). I primed it then set it to the on position and let it idle for about 5 minutes or so. It did not stall so I took it around the block and got on it a little bit. It seems to backfire just a little if I really roll on the throttle so the carbs might be off a little. It could also be that the tube I hooked up is a little bit streached. I got it from the battery acid overflow but it`s a little big. I guess a little air leak could cause a bit of a backfire. I will get the right tube and see what happens but I think my problem might be solved.Also I mentioned that there was a second hose coming from the engine block but it was actually just pushed between some other hoses and went to nothing.Man this reminds me of working on my old Porsche 914 LOL. i`M not sure if I loved my Porsche or hated it but I do miss it.