Bizarre, Strange, Weird timing problem, really need help!

[dougw2007]

I inherited this bike so don’t know the past. It had 91 k on the clock so I figured engine might be toast.

I started checking and found that most of bike was not in too bad a shape, probably stored indoors.

I had spark on cyl number 3 only and the gas didn’t smell bad, chokes worked and throttle operated fine.

I figured I would get a baseline and see what happens with some ether and a battery.

At first it would only fire on the one cyl and run maybe ten seconds. Then it did run and peaked up at a few thousand rpms and ran enough to blow out some fogging oil.

Then it died and this is where it gets interesting.

I put the compression gauge on it and got maybe 5 lbs on each cylinder. That is odd because with the plugs in, the starter is definitely under a load four times a revolution, but wings the engine over nicely when the plugs are out. Putting finger down a plug hole also results in feeling nice compression.

So I put the leak down gauge on it and turned the flywheel nut counter clockwise. If I put in 90 psi and rotate till both valves close the leak down gauge reads about 84 to 86 psi on each cylinder and it takes a good effort on a cheater bar to turn it to tdc against the air. No air is leaking out the oil fill or valves. This is about 5 % cylinder leakage.

Another note is as I was investigating all this I noticed red sealer on the engine halves and other places. So someone took the engine out and did something to it. Rebuilt it ? Fixed a gear problem ? Don’t know.

So I am frustrated at this point but can’t let go of the problem. I took the valve covers off and everything looks great in there and there is no looseness or play in the timing chains. I am not up to speed on these engines but turning the engine at the nut means an exact movement at the cams, no play or slop.

If I look down at the piston 3 and turn engine counter clockwise and watch the piston go up and down this is the result.

Crankshaft is at t2 and piston at the top of stroke. front cams small dots on lines. As the piston descends the intake opens, piston reaches bottom and as it starts up exhaust opens, at the top of stroke both valves are closed and piston descends and then it hits bottom and starts up both are still closed.

It now comes up to top and it is at t2 and starts cycle over again. Well, anyone can see it is not going to run like that.

The other side of the engine at least tracks like a four cycle engine in the proper sequence. On cylinder 3 and 4 the intake does not proceed a compression stroke but is followed by an exhaust stroke. Intake and then exhaust.

I did check the cam timing by setting the dot on the rear cylinders to the small dots at top dead center line on flywheel. I think the intakes on the rear cylinders might be off one tooth but that is a smaller matter. I rotate 360 and then 70 more to T2 and the dots line up on the front cyls.

A couple of things I wonder about.

The cams with the round ends with dots are on the right side of bike on the rear cylinders and they are on the left side of the front cyls? Could they be in backwards? Probably not. Could the cam gear on crank slipped or spun? The chain is nice and tight and I don’t see how it could be that far off. The cams have ex and intake stamped on them, they seem right. I put an allen wrench in the cam sproket hole and tried to turn engine, lightly, and it would not turn.

I could possible see that if the cams were way off then the compression might be low but how can I explain the 5 lbs of compression on the rear cylinders? I took my compression gauge out to another car and tested it there and it works just like it always has. How can a cylinder hold 90 psi of air with a leak down of 5 % so it has 86 psi of air in that cylinder and then have 5 lbs of compression? I can hardly turn a 2 foot breaker bar into the air pressure.

This engine has the YICS but I don’t see that effecting this.

I don't see any evidence of water in the oil.

If there was no carbon on the valves I would think that the engine was rebuilt wrong and never ran. But I did get it to run and the valves have enough carbon on them to indicate the engine ran. I am really baffled over this. I think judging by the leak down that the engine might just be good if I could figure this out.

Is it possible on these engines that the crankshaft is in two pieces and it has spun or moved?

I just can't see any reason for zero compression on all four and having cylinders 3 and 4 not have the proper sequence of intake compression exhaust.

Thanks for any input you can give me.

[Flyinfool]

First off, welcome to the forum.

 

It is always helpful to mention the bike that you are working on, Saves us from have to figure it out.

 

As far as being worn out, unless it was abused and not maintained, 91K is no where near worn out for this engine. There are some members here with over 200K and even a few with 300K.

 

The 83,84 and some of the 85s have an issue with 2nd gear going out due to a thrust washer that is not properly hardened. To fix this requires that you split the case. This could be a reason for all of the red sealant that you see. You do not need to pull the top end apart to fix the 2nd gear issue, so if that is what was done then the cams should not have been touched.

 

As long as you have the valve covers off, check the valve clearance to adjust if needed. The way this engine works is the clearance gets tighter with wear until it gets to zero and the valve will no longer close.

 

You mentioned that you had spark only on #3 . I would start looking there. You can disassemble the spark plug caps and inside there is a resistor, this is known to get corroded and block the spark. clean up all the parts and retest for spark.

 

As for your cam timing issue, I have to go back and reread what you wrote a couple more times to fully understand what you are seeing.

[BlueSky]

I don't think it is a good idea to put your finger on the spark plug hole with the engine turning. If your finger somehow got sucked into the head, you could be in a heap of trouble.

[dougw2007]

Thanks for the reply Flyinfool,

 

I went out and did some more testing and got one thing cleared up. My expensive OTC compression gauge was not working correctly. I switched to a second hose on it and now it reads fine. The check valve must be stuck or broken in the base of the hose. There are two hoses in the kit. That one thing was really throwing me off. There is nothing like a couple of things going wrong at once. Now I tested and I have 175 lbs compression in both rear cylinders.

 

I went through the ignition with a test module and I think I have figured out that the color code on the trigger coil wires are this: Orange is 1 cyl, white with red is 3 cyl, Gray is number 2 and white with black is number 4. If someone knows this they can comment on it being right or wrong.

 

So after figuring that out and getting good compression on the rear cylinders I have traced it back to what maybe the problem. Or wishful thinking. Is it possible that the intake cam could be installed 180 out? From just looking at the way the piston moves up and down and the exhaust cam I think that if I could do a 180 on the intake it would be closer to what I need.

 

So does anyone know if it is possible to just somehow loosen up the chain or the bolts or both and flip the cam? From looking at it it looks like this could be done. I don't want to mess with it yet until someone can advise me as to what the ramifications could be. With the pressure of the valves on the cam I don't know if it could be turned very easily.

 

I will read again in the shop manual how to set the cam timing but when I checked it before it was indicating it was correct but I must have missed something.

 

Thanks again for the help on this.

[bongobobny]

Check out our Read Only Tech section, there you will find complete wiring diagrams, both factory and a "simplified" version done by one of our members. There is also a thread there where you can download the factory service manual, etc.

 

Yes, as Jeff said, I would start with getting spark on all 4 cylinders! There are several things to look at! As Jeff said, look at and disassemble the spark plug caps! Then unscrew the ends that go into the coils and look for green inside the coil, they get corroded in there quite often. Cut about 1/4 inch off the end of the plug wire before reinstalling and push the rubber o ring on the plug wire up away from the end a little. Those O rings keep the wire from vibrating loose from the coil. The TCI unit may also be defective, they are known to have problems.

 

As far as cam timing and whether or not the cam is in backwards, consult the official Yamaha service manual for this information, or, there is a great video out that you can purchase from Damon Ferraiulo concerning complete engine rebuild...

 

http://www.venturerider.org/forum/showthread.php?84030-DVD-of-1st-gen-motor-amp-carb-rebuild-process-purchase-info

 

His videos are extremely informative!! They are for the VMax motor but it is the exact motor except on the heads the valves are bigger and the cams are hotter. The assembly, to include setting up the cam timing, and which way they go in will be on that video.

 

Good luck and we hope we can be of assistance to you, just ask, eventually you will get an answer, and usually it is the right answer!!

[videoarizona]

Douglas, first of all... You are way beyond me in terms of engine knowledge... So hope you will stick around to help out the rest of us not quite so knowledgeable!

Second, I know this is a simplification... But unless the PO did a rebuild... Which is doubtful as these engines are bullet proof usually... I would tend to think the cams are good. What has been done, however, by some of the best of us... It's to forget which cylinder is which. So... dumb question for ya... Are you sure you know which cylinder is #1 ,#2 ,etc.?

 

#1 is rear left, #2 is front left, #3 is rear right and #4 is front right. Can be confirmed with wiring diagram colors for tci and coils as well. I ask cause misidentifying a cylinder could explain why cams seem weird. Told ya it was a dumb question!

 

Seriously, I'm going to follow this thread as it sounds a good learning experience for me. Thanks for sharing!

Edited May 2, 2016 by videoarizona
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[dougw2007]

I got it fixed! It was really not that hard of a problem it was just my mental approach to getting the bike running and the strange action of the compression tester.

 

I was told that the bike was a 'ran when put away' bike and then would not start now. So I concentrated on the lack of spark. Then the compression read 5lbs and there was other strange behavior. I thought that I had it running for a minute or so but it must have been on just two cylinders.

 

What i found was that PO must have done a lot of work on the engine and then it NEVER RAN. The Intake cam was set up with the small hole instead of the large hole. I switched it around and it now has 200 some lbs of compression on the front two cyls. I don't know when I will be able to run it as some things are coming up this week but maybe in a bit.

 

Appreciate the help I found here and it is a fantastic technical library and resource.

 

Doug

[bongobobny]

Welcome aboard!!