[Blake9771]

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Hey, everybody! I hope I have come to the right forum for some help because I could really use it! For some time now I have been rebuilding the pistons on my buddies bike he had recently bought, a '93 XV535. He had brought it to me complaining of lack of compression, he had done some troubleshooting of his own and told me it was a cause of worn pistons rings. Taking his word on his diagnoses we had gotten to work tearing down the top half of the motor.

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After waiting many moons to receive all new parts for the build it comes time to put the motor back together. However we are still waiting on the head gaskets as they re on back order. I decided to take the time to make sure the cams had been set with the proper timing for the rebuild.

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Looking in the Haynes manual the cams should be aligned with the small punch mark on the sprocket aligned with a arrow in the cylinder head. However when I attempt to turn the cam to align the marks about every quarter turn of the sprocket causes the valves to push back on the cam spinning the cam to a position where the valve is closed. Throwing the marks out of alignment and loosening the cam bolt.

http://imgur.com/a/Bels2

 

[Blake9771]

Sorry about the bad formatting, it makes it kinda tough to read if you ask me. Also, I am attempting to get a link posted to this thread containing pictures, so bare with me!

 

[WintrSol]

Note that the photo in the book shows it with the chain on, which helps keep the cam from turning. You will probably have to make a tool to hold it in place while you attach the chain, like a spanner. A length of wood, with dowels (or bolts) in holes drilled to match two of the holes in the sprocket will work; just mate the dowels to two opposite holes, and hold the board with the marker aligned, against the spring pressure from the other valve that is open. You may need a third hand to hold it, while the chain is attached.

 

[Blake9771]

Smart thinking WintrSol! I greatly appreciate the response. I may have to give that a go, but let me know what you think about this. I was working at pulling the valves out so I could lap them before final assembly after taking toe rockers off I thought maybe I could pull off both rockers to take off any pressure on the cam. Install the chain to both heads with the crank at TDC and the marks on the sprockets aligned. Once the chains are on with the correct timing I would just reinstall the rockers like normal?

 

[Blake9771]

Also, if anyone could give me some insight as to what marks need to be aligned that'd be great. I had assumed the punch marks on the sprockets would face the sort of arrows or pointed edges around the outside of the housing?

 

[WintrSol]

I was considering adding that you could take the spring pressure off the valve that was pushing the cam away from the TDC mark, but thought that was a bit extreme. I don't know how hard that would be to reverse, once the head is bolted down, but it is an option.

The photo in the manual shows the punch mark in the sprocket aligned with the cast pointer at the top of the arch, which is clearly visible at the top of your first photo. I'd go with that. Before crimping the link in the chain, though, I'd carefully rotate the engine, and check the operation of the valves on both cylinders, just to be sure both sides are properly closed at TDC for each. My service manual has diagrams for valve open/close timing; if yours does too, it wouldn't hurt to check, before making the chain installation permanent.

 

[Unkle Krusty]

Cam timing.

Probably too late now, but with the head off you could find TDC with a dial gauge, and use a degree wheel on the crank. With just the inlet valve connected on number one cylinder, you can get precise cam timing, if the work shop manual, or the cam builder would give you the info.

Just checking my Yamaha book. It says to line up the dots. There is a disc / wheel on the crank with marks on it.

Unkle Krusty*

 

[slumlord]

Probably too late now, but with the head off you could find TDC with a dial gauge, and use a degree wheel on the crank. With just the inlet valve connected on number one cylinder, you can get precise cam timing, if the work shop manual, or the cam builder would give you the info.

Just checking my Yamaha book. It says to line up the dots. There is a disc / wheel on the crank with marks on it.

Unkle Krusty*

I have held the TDC marks steady on the crankshaft timing marks by placing a wrench on the crank bolt and using a hydraulic jack to precisely hold resistance against the wrench to keep the crank from turning. Sounds crude, but it works for me.

 

[Blake9771]

Hey! Thanks for all the replies guys, I forgot about this thread for a while! However I got it back together, with (what I hope is) the correct timing. I went with my original idea and put the timing chain assembly together with the marks on the rotor lined up with the cam sprockets in the correct position as normal. I had the rockers off the cam for the time being allowing the cam to spin freely. Once the chain was in place and tightened up I replaced the cams and it seems to have worked just fine! Thanks for all the help guys!