Motor job, or swap?

[easternrider]

When I bought my bike, it "supposedly" had 23000kms on it. Now it has 31000. Two seperate mechs. told me in their opinion that was probably correct. Anyway, just lately, I came to find out that I have low compression in the #2 cylinder. Did a wet test, compression went up. Even did an air test, which to me, points to a bad set of rings. I also recently bought a parts bike (all in pieces) and the motor has 52000kms on it, and not sure if 2nd gear works or not. I am now at the point where I can't spend a lot more on my bike. So, my question is: What would you do?

Pull my motor and replace the rings, or just do a swap-out with an unknown motor.

PS: the second motor does turn over, and will check compression before doing anything, if I can........

[DragonRider]

You dont have to worry about the tranny if the engine is an 86 or later, that problem was addressed in the 85's about mid year of that model year, later models dont have any problems with the transmisson. So if it was me and the engine was an 86 or later, I would do the swap if it runs. Another plus is your bumping the engine up another 100cc's if yours is a MKl. Good luck with whatever you do, and remember to pay attention to details and parts when dis-assembling.

QUOTE=easternrider;773064]When I bought my bike, it "supposedly" had 23000kms on it. Now it has 31000. Two seperate mechs. told me in their opinion that was probably correct. Anyway, just lately, I came to find out that I have low compression in the #2 cylinder. Did a wet test, compression went up. Even did an air test, which to me, points to a bad set of rings. I also recently bought a parts bike (all in pieces) and the motor has 52000kms on it, and not sure if 2nd gear works or not. I am now at the point where I can't spend a lot more on my bike. So, my question is: What would you do?

Pull my motor and replace the rings, or just do a swap-out with an unknown motor.

PS: the second motor does turn over, and will check compression before doing anything, if I can........

[easternrider]

No such luck there, the bike that I got for parts is 84 VR. I have been doing a lot of looking around, trying to price gaskets/parts, and just looking at the work involved in the tear down. Big job either way.

[bongobobny]

Yes it is! If you can get the spare motor running then use it so you can keep riding while you tear the problem motor. It is odd to hear of your issue as these motors generally are bullet proof and it should be nothing to get 20000 Km or more from them.

 

While you have the engine apart you can do the 2nd gear fix as well...

[frankd]

With only 31,000 KM (20,000 miles) on your 84, your rings aren't worn out. You probably have a stuck ring. Maybe you could free up the stuck ring by soaking it in Marvel Mystery Oil or something like it. Yamaha makes a treatment they call "Ring Free", but that might only free rings in a 2 stroke motor. ( I have used it to clean out my combustion chambers on my 1200)

 

However, 1200 pistons and rings are no longer available from Yamaha. If you have your heart set on rebuilding your old motor, maybe you could go to a cooperative Yamaha dealer and on his computer he can look up if the rings and pistons are in stock in any Yamaha dealer (at least this works here) and then you could buy them. It's a slim chance though because they have been out of stock for a long time.

[easternrider]

With only 31,000 KM (20,000 miles) on your 84, your rings aren't worn out. You probably have a stuck ring. Maybe you could free up the stuck ring by soaking it in Marvel Mystery Oil or something like it. Yamaha makes a treatment they call "Ring Free", but that might only free rings in a 2 stroke motor. ( I have used it to clean out my combustion chambers on my 1200)

 

 

I figured that after putting 8000kms on the bike, along with 1 1/2 cans of seafoam that if the rings were stuck, they would have come unstuck by now. (but not sure). Someone suggested putting transmission oil in there to help loosen if this is the case. On the other hand, it could be 131,000kms with worn out rings, and or cylinder(hope not). Anyway, I am trying out as many options that I can find, as I really do not want the trouble of tearing out the engine. I have too much to do now, and don't need the extra work.

[sandman]

Guess I didnt see leak down or compression results. What are other cylinders? A borescope of cylinder or even easier way to check wear would be remove a valve cvr and look at cams. Do a valve adjust while there if cams look good. Easy way to tell wear. And a good way to compare two engines of unknown condition. Good luck

[Venturous Randy]

When I look at a bike that I am being told is really low mileage, the first thing I do is look at the rotors. If there is a very noticeable lip on the rotors, I suspect the bike has turned the odometer over at least once. Sure, the rotors could have been replaced, but most likely, they haven't been.

RandyA

[GeorgeS]

Have you checked the Valve adjustment on that cylinder ??

 

Have you Run the bike for Several Tanks, of fuel, with a fairly heavy dose of

SEA-FOAM in the fuel?? ie: give it 3 or 4 tanks of fuel with heavy Sea-Foam dosage, and possible it will " free - Up " something.

 

Maby, Dirty valve seats ? Well, worth a try ??

[Flyinfool]

Even 131,000kms is not considered real high mileage on these bikes. that is only 81,400 miles.

[frankd]

Alex,

 

What prompted you to take a compression test in the first place?

 

Frank

[icebrrg3rd]

It comes down to this:

 

How many times do you want to remove your engine from the frame?

 

If you pull your engine and rebuild it, and also check (and fix) to make sure you won't encounter the 2nd gear issue in another year or so? That would be one engine removal and your bike will probably last a long time.

 

If you swap out the parts engine (w/o opening it) you might get a gem or a problem waiting to be discovered. That would be either one engine swap or 2 (or more) if issues pop up.

 

Now if it was me (not a lot of money, limited free time, and the know-how to pull it myself), I'd run it as is until I could save up a few bucks and search the interweb for a great deal on a newer known good running motor (because of the fixed 2nd gear and the extra 100cc), which is what I did for mine. I don't want to go back inside my motor ever again, I'll get a 2nd gen before I pull or split my motor again.

 

Good luck with whatever you choose to do.

 

-Andrew

Edited June 24, 2013 by icebrrg3rd

[Flyinfool]

 

Now if it was me (not a lot of money, limited free time, and the know-how to pull it myself), I'd run it as is until I could save up a few bucks and search the interweb for a great deal on a newer known good running motor (because of the fixed 2nd gear and the extra 100cc), which is what I did for mine. I don't want to go back inside my motor ever again, I'll get a 2nd gen before I pull or split my motor again.

Good luck with whatever you choose to do.

 

-Andrew

 

Say it isn't so.........

[icebrrg3rd]

Say it isn't so.........

All I'm saying is I'd get a 2nd gen instead of opening up my motor. Just stating how much I don't want to go back inside of my motor.

 

That said, I would most likely get another 1st gen IF I need a replacement IF my bike ever dies. I have a long ways to go before I go down that slippery slope of accepting that I'm old and resign myself to slowdom.

 

-Andrew

[easternrider]

Alex,

 

What prompted you to take a compression test in the first place?

 

Frank

 

The bike has been acting up, with a hesitation mostly when cruising. Engine will drop off, then pick-up, leaving you shaking back and forth. Before anyone says CARBS, they have been all redone. New gaskets, plugs, o-rings......

I have looked at so many things, that compression test was the next step

The compression in that cylinder stopped at 80 three times. Did wet test, up to 150, 2mins later 160

Edited June 25, 2013 by easternrider

[sandman]

Alex; please excuse my confusion, but I,m not following your comp tests. Are you doing a leak down? or std comp test? When you say wet do you mean you put oil in cylinder. What was difference in cyls? I,m not sure your symptoms are in line with a low cylinder. I would look for other contributing problems.

[dacheedah]

have u checked valves??

[easternrider]

Cylinder

#1 170

#2 80

#3 180

#4 150

Put oil down the #2 cylinder gave it a few minutes, and did comp. test. Pressure went up to 150. Waited another minute, tried again and pressure went up to 160. As I mentioned in earlier post, I also did an air test. Put #2 piston at TDC and hooked air line to the cylinder. No noticeable air came out of the exhaust, or the carbs, teling me the valves are good. Took the oil fill cap off, and air was coming out, so air was leaking out around the rings. Thus my conclusion that the rings are bad/stuck/worn/broke/PITA.....

[Big Lou]

if you can put compressed air into the cylinder on the compression stroke of the motor you will be able to tell whether it is a certain valve or a ring

 

air will come out the carb ,,or exaust,,, or the blowby tube that does into the air box,,

 

then you will know exactally what part is bad.. easy way

 

:lightbulb:

[easternrider]

if you can put compressed air into the cylinder on the compression stroke of the motor you will be able to tell whether it is a certain valve or a ring

air will come out the carb ,,or exaust,,, or the blowby tube that does into the air box,,

then you will know exactally what part is bad.. easy way

 

Not to point out the obvious, but if you look halfway through the last post you will see that I already did that

:As I mentioned in earlier post, I also did an air test. Put #2 piston at TDC and hooked air line to the cylinder. No noticeable air came out of the exhaust, or the carbs, teling me the valves are good

[sandman]

Alex; A leak down tester is generally used to measure rate of leakage. You can soak cylinder 24hrs with marvel mystery oil(warm engine if possible). That may free up rings. But I think you have another culpret. Good luck

[BlueVenture87]

If this were mine I would put the other motor in and call it good. It could be a good engine or bad. The thing is you can't tell ahead of time so worrying about it is somewhat a waste of energy. Swap it and ride it! Swap it and ride it while you repair the original. A swap is a big job but it's an old bike. Don't let better stand in the way of good. Ride it! You have done the tests and likely isolated the trouble on motor 1, try motor #2!

[RSTDdog]

if you are going to give a last attempt to soak with anything I would use Ring Free. If its a stuck ring from carbon build up it should free it up. I would suggest pouring it straight undiluted in the cylinder and let it sit over night. Then Mix the clean-up ratio in the gas tank with fuel and go run it. If that doesn't free it up, you will have to go in.

 

If you are going to swap motors, obviously do a compression test on the spare motor before doing the swap.