I need engine advise

[rjg1985]

I have a 1985 that starts and runs great, but it has a miss at idle. Cyclinder #2 has low compression (about 65 psi) I think it is the rings because after I put a little oil in the cylinder the compression went up to 100 psi. I can not find new piston rings anywhere. My question is do I replace the engine or just ride that way. It goes down the higway just fine and gets 38 mpg. I bought it last fall with 45600 miles on the odometer I'm thinking that was 145600 miles? The local salvage yards want $500 to $1000 for an engine. Does anyone here know of a source for rings for these bikes?

Thanks in advance for your help,

Randy

[mraf]

Have you checked the valve clearance? Synced the carbs? New plugs? Made sure the exhaust it not leaking? Bad coil? It just seems funny that you have bad compression on only one cylinder and not the rest. Being that the number 2 cylinder should have received the same amount of oil as the others during operation. You might try these guys Speed and Sport Yamaha toll free 866-701-3391. They have a huge parts inventory.

[rjg1985]

I have done all of those things except check the valve clearence. Cylinders #1,3 & 4 have equal compression but it seems low also all 3 are around 125 psi.

[frogmaster]

Randy,

 

Kinda funny that valves was the only thing not done.... "seems to be common" around here lately. By all means run a search on "valves" and see some great information by (Vgoose7)(spelling?) and some other not so great advice. Welcome to the site and there is no such thing as a stupid question.

[mraf]

Did you check with throttle wide open? Equal compression is good. Check valves. Sounds about the only thing left to do before the big bucks or tear down. These engines are made so that the valve clearance gets smaller with usage. My bet valve clearance.

[rjg1985]

I didn't suspect the valves because the compression came up with oil in the cylinder, but it is worth checking the clearence in the process of elimination. That would be great if that was the cause.

[Venturous Randy]

Your test of putting oil in the cylinder is a good indicator of a ring problem. What you may have is stuck rings. There may be some products out there that may help and you may even could pour some Sea Foam into the spark plug hole and let it set over night. That may break the rings loose.

RandyA

[RandyR]

Its not unusual for one cyclinder in any multi cyclinder engine to need rings, while the others are ok (or better).

 

I agree, the oil test you did is a good indicater of a rings problem, as you surmised already. But, you should check the valves too, just to be on the safe side. Same valve shims and tool for the 1st gen as 2nd gen (and vmax too).

 

I wonder if the rings from the 2nd gens would work on the 1300cc 1st gens? they seem to have the same bore/stroke.

 

http://www.venturerider.org/forum/showthread.php?threadid=39054

 

btw, I see a couple minor errors in this table.

[rjg1985]

When I bought the bike I rode it home 45 miles. The seller said he rode it daily, but the fork seals were leaking there were parts missing. The #1 carb's float was not working and dumping fuel down the throat into the cylinder. Since I have fixed all the obvious problems cleaned and synced carbs, replaced fork seals and other missing things. I put 3000 miles on it. I ran sea foam in the oil for about the last 300 miles before I changed the oil. The carbs were really gummed up so I think the bike had sat for a long time. I am going to try sea foam down the spark plug hole and let it sit for a while. I am open to any suggestions. Even with a weak cylinder this bike flies. I think it would be a blast with the motor at 100%. One other thing is the bike has a slight buzz vibration between 3500 and 4000 rpm smooth before and after. Is that normal for these bikes?

[frankd]

Depending on if your 85 is an early or late model, you may be close to another problem with 45K miles on the clock. The 83, 84, and early 85's had a soft shim in the transmission that lead to 2nd gear hopping out with about 60-75Kmiles. Some had this problem way sooner. I don't have the service bulletin anymore that lists the serial number that is the change over to the harder shim, I'm sure it's someplace on the site. A replacement 1300cc motor might be the best way to go if you're looking at rebuilding the transmission also. Keep an eye on E-bay. I saw one 3 or 4 weeks ago that was a low mileage 1300cc. It had an opening bid of $250 and nobody bit.

 

However, check the valves on that cylinder and make sure all 4 still have some clearance. You don't care how much (at this stage), just that they all have a little clearance. Also, check how much blow-by the engine has. If the rings are that bad, you should see it in the blow by. I seem to remember that the crankcase ventilation hose goes to the air cleaner box....find it, pull it off, and start the motor and watch if has a puff, rest, rest, rest, puff patern. If it looks pretty even and not excessive, the rings aren't your problem.

 

As for the vibration.....My 83 1200 wasn't prefectly smooth. Depending on the speed you could feel a little vibration here and there. Also the left rear crash bar showed vibration. I have noticed that my 89 1300 is considerably smoother. I'm not saying the vibration on the 83 was bothersome.....just that you could tell in a couple of places that it wasn't an electric motor. But if you do have a weak cylinder, it will vibrate more.

 

Yamaha makes "Ring Free" for stuck rings. I'd try a can of that before I tore it down. I used it on my 83 to clean out the combustion chambers. It did a good job for that also, but it fouled a plug. I couldn't get the insulator clean and had to replace the plug. The other 3 survived.

[rjg1985]

Thanks to all for the great help. I looked for signs of blow by and there is none that was good news. So I borrowed a leakdown tester set the #2 cylinder at TBC on the compression stroke added air pressure. Air was gushing out the exhaust valve. So I meed to check the valve clearence and should be good to go. When I did my compression test with some oil in the cylinder there must have been enough there to seal some around the valve to bring the compression up and fool me into thinking it was the rings. Again thanks

 

Randy

[rjg1985]

One more thing where is the serial # located on the engine? I would like to check which side of the 2nd gear fix I am on.

[Condor]

One more thing where is the serial # located on the engine? I would like to check which side of the 2nd gear fix I am on.

 

The Vin# is located on your title, and also the decal right under the clutch housing on the frame member. Anything over 1417 and you're good to go... If youwant to make sure the engine is original check behind the plastic engine cover on the left hand side rearward. There's a flat area that has the number stamped on it.

[rjg1985]

The good news is my engine is original, the bad news is the serial # 000214 guess I will deal with the 2nd gear when it starts slipping.

Thanks Again,

 

Randy

[Squeeze]

The actual Engine Serial# is visible from the left Side, behind the Plastic Cover on the rear. The # is above the Output -Shaft, there#'s flat Area in the Housing.

[rjg1985]

A local bike shop quoted me $150.00 to adjust the valve clearence on my 85. That sounds like a fair deal to me. Or does that seem low or high any opinions.

[RandyR]

A local bike shop quoted me $150.00 to adjust the valve clearence on my 85. That sounds like a fair deal to me. Or does that seem low or high any opinions.

 

Sounds fair. Or you could borrow a shim kit and tool from several people here on the forum and do it yourself.

[Squidley]

A local bike shop quoted me $150.00 to adjust the valve clearence on my 85. That sounds like a fair deal to me. Or does that seem low or high any opinions.

 

 

Thats not bad, as long as they know what they are doing. I would also suspect that you might have to replace the valve cover gaskets as you have to pull them off to shim the valves. Make sure that if you have them do it that they guarantee the covers wont leak. Otherwise have them replace the gaskets before they put it together, or find out if that price is with new gaskets.

[rjg1985]

I thought about doing it my self but by the time I bought the tool and possibly 16 new shims I wouldn't be any money ahead. The tool is around $40.00 and the shims are about $10.00 each. I didn't know anyone had a shim kit to lend out. Who has such a wonderful thing? And what are terms of use?

[Marcarl]

I thought about doing it my self but by the time I bought the tool and possibly 16 new shims I wouldn't be any money ahead. The tool is around $40.00 and the shims are about $10.00 each. I didn't know anyone had a shim kit to lend out. Who has such a wonderful thing? And what are terms of use?

Often times you can borrow a tool from your local bike shop\dealer, and can exchange the shimes as well. Depends on the shop, but some are willing.

[Dano]

There was a kit flying around here somewhere, I believe BuddyRich is the original owner. There are shims in the kit, but as I found out, it won't have the ones you need! Partshark.com (Flatout) has the shims for $8.98. Thats about 4 bucks more than I paid last year! If you are not sure of your capabilities in this, the money sounds like a good deal!

 

Dan

[Venturous Randy]

I thought about doing it my self but by the time I bought the tool and possibly 16 new shims I wouldn't be any money ahead. The tool is around $40.00 and the shims are about $10.00 each. I didn't know anyone had a shim kit to lend out. Who has such a wonderful thing? And what are terms of use?

 

The possibility of you needing 16 shims is about the same as me winning the Lotto, twice in a row. You may need a couple and you may also be able to use the ones you took out at a different location.

If you have a local shop, many times they have a stash of shims and will trade for free or very little. Even though I have traded shims at the Yamaha shop, I do better at the local independant shop. It is amazing that with 100,000 miles, these shims will still be like new. And, these shims fit a lot of different bikes.

RandyA

[rjg1985]

I think i'm going to let the shop handle this time because The #2 cilinder exhaust valve has no clearence to measure right now, it's slightly open that's why my commpression is low on that cylinder. I know the mechanic that is going to do the work so hopfully he will let me be there when he does it so I will know what I am doing next time. He also told me it should be checked again after 500 or so miles because there could carbon build up around the valve from being open. I will be able to do the follow up check.