1979 XS750 Special Project

So i recently picked up a 1979 Yamaha XS750 Special in pretty decent cosmetic condition. It had been sitting around for a year or so. When i picked it up we couldnt get it to start but the engine was turning over. I took her home and after charging the battery up, the engine purred to life. Well... i shouldnt say purred, rather sputtered to life. Anyway, it was warm enough here in central iowa last night to take her out for a spin just to see what i need to do before it can be in perfect running condition. I took it around the block and the first thing i noticed was the engine was just sputtering alot and had to be fairly generous on the throttle to get it going. Shifting wasnt that bad but it seemed like the carbs were really out of sync and just probably all gooped up. The clutch lever was super tight and it almost sprained my hands trying to pull it to shift gears. Brakes seemed to be ok. I think i probably was out for 10 minutes when i decided to return home. Another thing i noticed when i turned it off was a weird shriek, almost like a mechanical cough. I started it back up and it happened again when i killed the engine.
Heres what im thinking i should probably do:

Check all fluid levels and probably switch out the fluids
Adjust the clutch cable or try to figure out whats causing it to be so tight
Clean out the carbs and sync them

Anything else i should be doing?
I decided i should probably fix the damn thing before i start making any modifications...

 

may i ask, how much you paid?

 

Rig up a funnel and gravity feed oil thru the clutch cable, also, you could spin it with a drill (in the direction the cable is wrapped!),
* inline paper fuel filter
* new brake fluid
* clean - measure alternator brushes
* check - grease wheel bearings
* how's that fuse box?
* new tapered steering bearings ($40?)
How many miles are on it?

 

The clutch cable might be going bad on you. Try to lube like above mentioned. The mechanical cough you mentioned could be something loose with the exhaust. Give all the fasteners a quick check.

 

replace the spark plugs with NGK's. drain and replace the fuel. Check the condition of the spark plug wires and coils. Make sure they arent cracked. Maybe ohm them out also. Get the carbs totaly spotless. Make sure the carb boots are tight and not dry rotten and cracked. Make sure you run it with the airbox on. It will run terrible if the air box is off or if you have pod filters and it's not jetted correctly.

 

Thanks for the quick replies. Its a pretty slow day at work here so i thought I'd check if any body had replied and i was surprised at the number of responses/great suggestions.

Its supposed to be in the 50s this weekend so ill try and get some of the above mentioned underway to see what type of shape its in. Also, would it be a good idea to replace the oil in the front forks?

Crath - It currently has the stock air box but I do have some cheapo pod filters for it which i may or may not install later after i've cleaned out all the crap from the carbs. I do realize that it will require some jetting which is why im going to wait till i decide if i want to mess around with the exhaust or not. I do like your idea on your maxim for the exhaust but i might want them to be a bit longer and then header wrap. We'll see. I might also need your help with the struts i mentioned. Will keep you posted

As for fasteners lose on the exhaust ill check on that. But the sound almost sounds like it may be coming from the alternator? It almost sounds similar to when the engine turns over when i try to start it. Its just louder and more shrieky when i shut it off. Ill try to take a video of it if possible to show what it sounds like.

Schooter - i paid about $500 for it delivered to my place from a neighboring city some 50 miles from here. I will post some pictures soon, it looks fairly decent from the outside. No idea whats going on inside yet. Stay tuned...

 

Here are some photos of the motorcycle as of right now

 

i bought 2 of those , 1979's for 50$ each, sold them for $250 each. now i have an XS850 in the garage i bought for $50.

 

So i spent about an hour today trying to remove the carbs and i was finally able to manage taking them out. In the process i found out that the plastic connectors/boots b/w the carbs and the engine were just flaky as hell. They basically just flaked out on me and crumbled to their demise. Also, after going over the carbs a couple of time before i actually tore it apart, i noticed that one of the PO's might ahve tried to take the carbs apart or something. there are more than a few screw heads that are stripped out or completely gone. Im trying to find somehwere to find EzOut stuff. Anyone familiar with those or know where i can get some? i just need to find a way to get these stripped out screws out. Any ideas?

 

Also, has anyone used Sudco to order parts? I've found the part number (PN) for the carb joints to the engine. The PN is 2F3-13586-00
Sudco lists a set of for about $60
This website www.cyclewearables.com lists them for $48
Bikebandit has them for $40 each

Anybody have any experience with the above mentioned retailers?
Im not sure if Chacal is reading this but i read somewhere that he is fairly resourceful for parts. I believe this may not be a common part to the XJ but i was wondering if he would be able to use his resources to secure a set? Other than that im still looking at taking the stripped screws out to continue taking the carbs apart.

 

Some times I can use a small pair channel lock pliers to get screws broken loose.
Use a spray lube to penetrate the threads some.

 

Im going to try that tonight. I also read somewhere to give the screws a sharp tap with a hammer to release the threads from the mating sides incase they've bonded over the years or something. I also got some left hand drill bits coming in the mail to go that direction.
Curently working on the carbs and then moving onto the front forks. They need some attention.

I ordered some more parts including some drag bars and different grips.

Anyone need a windscreen or a seat? Im probably going to put them on fleabay later tonight...

 

Kroil has been mentioned here several times. Fitz has used it to free a bunch of stuck things. I have tried it on one thing and it works amazingly well

 

Thanks Bill. I'll check out Kroil today and try that too.

 

Had a 79 just like it with the same seat.

You need to look at that fuse box closely if not just replace it.
Those coils have a compression connector on them, make sure they are making good connection, Ohm out the coils with the wires and Ohm out the spark plug caps... Remake all the connections between the TCI and coils and pickup coils. Check the mechanical advance under the left side cover to be sure smooth operating. Might as well pull the valve cover and check valve clearances while your at it. Clean those Carbs good and set float levels correct. Make sure the Petcocks are working properly.

I saw a set(3) of those carb boots for $25 here: CarbKitCapital

 

rpgoerlich: thats great advice. I checked on the fusebox and it seems like everything is good. I am considering changing the fusebox (i saw a very good writeup somewhere regarding changing the fusebox. Currently trying to remove some darn screws/bolts with stripped heads. Trying some penetrating oil to loosen them up.

 

Penetrating oil worked on 1 screw. The other 2 are pretty stuck in there. Saturated them with the oil and am going to let them sit for a while before i take a crack at it again.

Also, does anyone know the PN for the screws that go into the choke lever? The screws im talking about are the screws that hold the small bracket which manipulates the choke plungers in each carb. Those are the screws that are busted and the heads are completely destroyed. Will need to replace them. Any ideas where to get replacements? I tried looking up the PNs from the parts manual but cant find the screw.

 

I'm assuming that your choke lever pushes down to activate. If so those are MIC I Carbs. The screw(15) is still available for about a buck, but the ring that goes behind it is not. Might find one off a set of parts carbs

That 79 SF should have had MIC II's on it with a choke lever that pulls out to activate.

 

Yea i have the MIK II carbs. It took me forever but i finally got my workshop repair manual for the xs750 and finally found a clear picture of the component parts list for the carbs. Anyway, the screw itself is not available anywhere on sale. But i found a carb repair kit which contains this screw and i needed three. Each kit is $15 (ouch!) but i guess its a good thing since the kit includes all needles, jets, gaskets and screws for each carb body. Also ordered the carb holders/boots from here. Carkitcapital.com good site for parts and stuff.

 

so... alot of stripped screw heads are putting a wrench in progress... and making me frustrated. damn...

 

A small pair of vice grips makes quick work of those stripped screws...
Of course you'll still have to replace them.

And by the way since it's an XS750 there's a good site at: Yamaha-Triples.Org for alot of good info.

 

does that bike have a dual front disk?

I don;t know if this has been discussed before, but does the front end swap over to the XJ650 in any way?

 

It does have a dual front disk. However, i am oblivious to it being able to swap over to the XJs...

 

Just finished cleaning out the carbs and using the rebuild kits to replace all jets, gaskets etc. I raised the needle up one notch to cater for the installation of the pod filters. Im goign to try them on tonight. Its been fairly cold here in Iowa for me to work outside.

 

i had sometime this weekend to go back into the garage in the crappy cold weather and try to see if the carbs work. I had cleaned them and rebuilt them using rebuild kits and installed brand new boots between the carbs and the engine. Now the damn thing wont start. I got a little discouraged and just went inside since it was too cold.
Any suggestions as to where to start looking for whats wrong? It started right up before i took the carbs out. Now that iv'e cleaned them and replaced parts with new ones, the engine just turns over but doesnt start...
I'll keep fumbling with it but any ideas would be great. Thanks...

 

Hmmm... I'm sure the experts will be along any minute, but my bike will often turn over but not light up if the battery is low. (Something to do with enough energy to run the starter, but not the sparks too). So, if it took you a while to do the rebuild on the carbs, perhaps the battery needs a charge. Maybe something to check (easy) before you dig into the carbs again.

 

Good idea. I did recharge the battery a while ago but i guess it wouldnt hurt to try again. Its going to be in the 50s here this week so ill probably find some time to try working on the bike again.

 

So after about a month of no progress, i just spent some time with a friend of mine who builds really great choppers from Xs650s for some inspiration. I guess it worked. I came back home and tore apart the old handlebar and replaced the new drag bars i got a few days ago. However, my bike wouldnt even turn over. I realized that the controls werent making a decent ground with the bike so i took the controls off and manually grounded the button to the frame and lo and starts!!!
However, ran into a few snags which i intend to check out soon. Some of which are:

1. motorcycle stuggles to start but will after a while with full choke on. Choke closed and bike dies. Corrective action? I put pods on, should i raise the needle one more step? (i already did for the pods when i cleaned the carbs out). I believe my mixture screws might be screwey ever since i rebuilt the carbs.
2. My bike when running, with choke on, would backfire sometimes when i would pull the throttle... air/fuel mixture not good?

any ideas/insight would be helpful!!