1981 XJ650 Stock Project Build

Did this ever get done?

 

proper routing is essential lube the cable well and a proper adjustment and the clutch is a heavy pull

 

5 turns out on mixture screw is going the wrong direction


Float levels were set dry to 17mm when I rebuilt the carbs.

setting float height is just a referance point for when you do a wet set

before you remove the carbs do a wet test it is the ONLY way to set your fuel level

this link tells you how and gives specs for your carb -Fuel level measured via the clear-tube gauge: 3mm +/- 1mm (.12 +/- .04 inches)


Setting the fuel levels



ignore specs in photos your specs are -Fuel level measured via the clear-tube gauge: 3mm +/- 1mm (.12 +/- .04 inches)

 

Kmoe, I didn't replace the throttle seals nor the fuel rail o rings, although the carbs aren't leaking from the fuel rail.

As far as the carbs go tomorrow, I'm planning on taking wet float height measurements and then removing them and taking them apart to see if I put anything back in the wrong spot.

 

make sure that you can spray carb cleaner into the well in the side of carb bowls and fluid comes out of the tiny hole inside of the carb bowls. (enrichment circuit)

also did you soak the rack in carb cleaner if you did that the seals are likly shot
I think from your photos you did not break the rack.

it is encourgageing that with a leaky tester you got 120psi

 

I did not soak the rack, although I soaked all the jets, float bowls, screws in kerosene. Then used brake clean to remove the oily residue and any remaining residue buildup left. If I remember correctly, I remember making sure the enrichment jet/tubes were all clear, but maybe I didn't. Also hoping I have the pilot jets in the wrong place at this point. Honestly I'm wishing I messed up cleaning the carbs royally the first go around because it'll make it that much more likely to work this time lol. I'll post back tomorrow with my findings.

 

Took the carbs apart today, everything was still nice and clean, nothing clogged up and nothing that I missed the first time around. Pilot jets in the right spot as well. What I did manage to screw up was the float levels. When I originally set them I measured one carb out to 17mm and matched the rest by eye. Upon taking them apart, I realized I must've had one too many beers when I was doing it because none of the floats were set at the same height. The one carb I initially set by measurement was spot on with the float height, the rest were all too small with anywhere from 2-4 mm low, numbers taken from a wet measurement. Hopefully when I throw the carbs back on this solves the starting problem.

 

So good news and bad news. I finally got the carbs figured out. It turned out all that was wrong was my floats were way off. Got them adjusted to 3mm on all four. Threw them on the bike and viola, good to go, right? No. After letting it sit idling for around 10 minutes, I figured the smoke was from the exhaust system being freshly painted (forgot to update a little while back, muffler was broken in half, welded it all back together and coated with exhaust paint) and it being the first proper start in the last decade. Shut it off and let it cool for 30 minutes, then fired it back up again. Let it idle for another 10 minutes and it was still smoking bad so I shut it off and noticed the head gasket was bubbling oil pretty much all the way around the whole gasket.



Also when I changed the oil, there were metal flakes in the oil that I had high hopes were from the transmission, but with that and the leaking headgasket, it's looking like it makes more sense to swap the YICS motor from the second bike instead of tearing this one apart.

On the bright side, I got the brake master cylinder and caliper rebuilt, so theres that (no pictures unfortunately, . Also, here's some pictures of the exhaust work that I never posted.



And a video of it running
Video cuts out when my phone ran out of memory lol

 

So I started getting to swapping the YICS motor in. Pulled the YICS motor out of the '82 in my yard before the Superbowl started. Threw down a blanket in the yard and took it out with the bike on its side



Cleaned the engine up with some degreaser and a wire brush and figured I should check the valves while I had such good access.
When I pulled the valve cover, I found that the timing/cam chain was loose enough to score the top of the valve cover.


The engine has an automatic cam chain tensioner, is this a part that tends to fail or is it more likely the chain stretched too much? Is it a direct replacement to take the manual chain tensioner from the '81 engine and throw it on there? I'd honestly prefer a manual tensioner if possible, for the same reason I prefer locknut and rocker valves.
Procedure to take the tensioner off is set the engine to TDC on piston 1 and then just pull the thing off? Here's a picture of the tensioner I'm working with.


Checked the valve clearances and here's my results

Seems everything is in spec except my 2nd exhaust valve needs to come down a shim size. I'm worried that, considering the tolerances seem like a valve job was done recently, coupled with the cam chain scoring in the valve cover that maybe the E2 valve may be bent slightly due to the chain coming too loose and the valve said hello to the piston. I'll be doing a compression test soon enough to check this, hopefully the previous owner just put in the incorrect shim and all I'll need to do is switch it out and everything will be all good.

Today consisted of stripping everything off the bike to get ready for engine removal, driveshaft u-joint bolts, CDI/rectifier plate, battery and box, airbox, exhaust, carbs. Unfortunately, up here in Seattle we got a bunch of snow on Monday so pulling the second motor will have to wait until the snow clears up.

 

there is a mark labeled c for cam chain tensioner neat the tdc mark use the c mark

the 82 cam chain tensioner is used in 81,82,83 650 ans 750 bikes http://www.partzilla.com/parts/detail/yamaha/YP-5G2-12210-02-00.html

could be it is stuck or that the guide it presses against is worn.

 

That is an expensive piece of kit for something so small! I'll pull it off and see if it's the guide or the tensioner that's the issue. Any idea if I can direct swap a manual tensioner for the auto one that's on there? It looks like I can, but I'd be a whole lot more confident if I'm not the first known person to try.

 

The earlier manual tensioner is a direct swap. The auto tensioner may just need to be taken apart and degunked/reset.