HELP 2 BIKES

Ok so I have a 1982 Yamaha xj550j and a Yamaha xs650 the 550 is chain driven and the 650 is drive shaft is there a way I can swap the engine from the 550 onto the 650 frame and drive shaft the 650 won't start has bad compression haven't even heard it start the 550 runs great but back brake lever if I press the back brake get stuck and locks my tire I have no clue how to fix that but the 650s back brakes work great again the 550 is chain and the 650 is shaft plaza help

 

Black is the 550

 

Red is the 650

 

Why don't you pull back wheel off of 550 and replace the brake shoes ....all you have to do is slack the chain adjuster off if your concerned about the chain. This would be far easier than trying to swap swing arms and engine etc . Brake shoes are cheap and are a definite maintenance item . As to the bike with low compression , before writing it off , try another gauge , make sure you have a fully charged battery , throttle wide open when cranking and all 4 plugs removed , a little oil down the cylinder to see if it reads higher. Agree if it is lower than 100 psi it is low , but also could mean valves are tight and need shims adjustment or bad rings ..if it is zero then you probably have a hole in a piston .

 

The bike with the low compression cylinder 2.3.4 showing 130psi the first cylinder 60 psi. Did the oil thing and it jumped up to 89psi I'm pretty sure the piston is shot now as of the back tire on the 550 is that all it could be is the brakes?

 

I have never heard of anyone swapping a chain drive engine onto a shaft drive transmission, but I have to assume it would be FAR more complex than a drum brake service/rebuild. Sell the 650 as a parts bike and use the funds to fix the 550. Or sell.the 550 as an easy project, and buy another xs650 and you have a part bike.

 

I recommend replacing the brake shoes, cleaning the drum, as well as removing/cleaning/lubricating the pivot points for the rear brake. The one in the backing plate and the one in the frame that the pedal connects to. My pedal would stick and that's what fixed mine. I replaced the shoes under advisement here to avoid the linings delaminating and causing a rear tire lock up that pulling in the clutch won't fix.

 

The 650 is a parts bike now the only thing that I can't use is the engine and shaft everything else fits the 550 runs perfect like brand new all except the back tire locks when I brake I didn't realize it was as some as replacing the brakes

 

There is an excellent write up on here about replacing rear brakes that I'm sure someone more tech savvy than I could link for you

 

The rings in the 650 are likely stuck. That along with valves out of adjustment would account for the low compression. Soak the two low cylinders in a mix of 50% ATF and 50% Acetone to free up the rings. Alos double check wth another compressin gauge. Over the past year we've had lots of posts about low compression that turn out to just be faulty gauges.

The engine swap that you propose is only possible with fairly extensive modifications to a critical area of the frame, and should not be undertaken unless you have done such work before.

BTW, your assertion that everything else from the 650 fits the 550 is entirely inorrect. There are very few parts that swap between the two.

Start doing your homework here: The Information Overload Hour

Then:
Bigfitz's AIRHEAD VALVE ADJUSTMENT with Pics - parts I & II

Why you need to rebuild your caliper and M/C w/pics

Rear brake rebuild - 550 Maxim

 

One other item have you checked the rear brake adjustment pointer? Push on brake pedal at the pivot arm on backing plate is a scale of it is at full travel then shoes are shot ...either way pull rear tire and check brake shoes even if they look good ...replace your safety is more important than savings a couple of bucks. Xj4ever has correct brake shoes, or eBay your looking at around 20 to 30 bucks cheap to get it working a locked up rear wheel is not cool.

 

K-moe you are right and I have done many mods on bikes so I'm pretty sure I can do the frame change I appreciate your input though and with the parts being the same for the most part everything I have took off the 650 and put on the 550 match up perfect and working down to the wiring harness honestly I have just never had a back tire lock up when pressed the pedal that's where I'm at now but I was able to pull both back tires off and bought a sprocket to fit and the tire was able to switch brakes work with no problem couldn't be happier thanks for the input guys

 

I just don't get the point of taking the engine from a lightweight and putting it into a middleweight.
Even accounting for engine weight, the resulting machine will be down 20 horsepower, and not lose enough weight to make up the difference.

 

It was just a thought since I'm pretty much down to a frame now I just really like the frame but love my 550 so I was wondering if anyone knew to be honest I'll probably end up rebuilding the 650 over the winter