My vintage bike project-75 yamaha xs500

86 Fox

Forum Member
I know i've posted a few threads here and there with photos and updates about the bike so i figured i may as well post an official build/project thread about the bike and the issues i've been having with it to see if anyone can throw in there $ .02

heres what i just typed up and sent to MotorPsycho (the guy i bought it from on here)


I'll give you the step by step of whats been my experience with it so far:

the first day we tore it apart, cleaned the carbs out like crazy soaking all the jets in octane gas and using an air compressor to dry them and blow out all dirt, and the left cylinder fired up, but not the right. So we bought two new spark plugs and both cylinders fired up perfectly and the thing sounded like thunder in a garage.

Once we got it started we took it around the block, and it would go on both cylinders until about 3k rpms and the right one would cut out, so its top end was about 35 mph in 4th or 5th gear, so i rode it about a mile home to my house from my friends where we had room to work on it and it sat for a couple months when it was just too cold to get motivated to work on it.

I kept the battery inside once i realized the cold was killing it and it needs to be recharged since i still have to jump it from time to time to get it started and even though the electric start is rough, it still gets the job done when its hooked up with cables.. once its warmed up i usually kick start it.

but warm weather came so we tore it back apart, re-cleaned the carbs even better, took the diaphragms on top apart and saw i was missing a gasket on one of them, and that the intake manifolds were covered in a gray silicone type material around the seals and the rubber was all chipped up so we thought maybe air was getting in and not allowing the correct air/fuel mixture, that wasn't the case either.

So i bought carb rebuild kits for a 1974 tx500 and they worked perfectly on my 75 XS, put them back on and the bike ran better, and had a much healthier idle, but now at about 4500 rpms it does the same thing, cutting out and running on one (the left) cylinder.

i ordered new intake manifolds off ebay and put those on and like i said it still did the same thing, so now im at a loss for what else it could be.. im thinking its something in the valves or possibly ignition but my knowledge of bikes is still relatively limited and i'm considering taking it into Ricks custom cycle and just having that shop fix it and paying them, cause frankly.. i just wanna ride the thing lol i dont care what it costs anymore.

heres some pictures of my progress so far maybe you can diagnose the issue from what i've told you, let me know if you wanna know anything else that i didn't include.

First night comin home
TripHome.jpg

Fuelin it up after it fired up on both cylinders at my friends gettin ready to take it around the block
FirstFuelUp-1.jpg

Jumping it during the colder months just to start it once every few weeks, before i took the battery inside
Photo0743.jpg

Just lookin pretty :D
yamaha1.jpg

Keyster Carb rebuild kits-30 bucks for both (ebay is the best)
Photo0948.jpg

Older silicone covered chipped up boots/manifolds
Photo0964.jpg

New intake manifolds (used but in better condition) 15 bucks online
Photo0965.jpg

as it sits not, just waiting to be ridden
Photo0934.jpg
 
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