Bad News... and I am not talking about the Bears

[Huron52]

Saturday night when after riding the bike for about 180 kilometers. I started it up after sitting for about 1 hour. A very bad rattle appeared and won't run very well, then quit.
I think I have made some contact internally with some motor parts.... Pistons to valves.

Now I poss this question...Parts ... Can I get valves, guides and cam train parts to rebuild?

If figure at this point in the season I am done riding so I have the winter to tear down and rebuild. When I open it up How far do I go. If the pistons are damaged is my only route big bore?

If that being the case should I go the route of what Merriam cycle does? ie big bore, bigger coils, rejetting?

It only has 66,000 kilometers on it.... 40 some thousand miles

I would like to here from you people.... as to opinons

thanks in advance...

[Snow]

Yuo might try making sure that it wasn't just your cam chain tensioner getting loose on you - I've had my..well..not quite right before and the bike made the most incredibly horrible noises and I thought I was screwed, but then followed the adjusting procedure and all was pretty much well

[skids]

Take off the "valve cover," remover or loosen the spark plugs, and remove the timing cover. Rotate the crank clockwise more than a revolution with the "nut" on the end of the timing plate, and stop when it is at top-dead-center (T-mark). Check to see if the marks on the cam bosses (arrows I think) line up with the dots on the cam shafts. If they don't, you probably have a bent valve or two. This is usually very fixable with new valves, lapping compound, and a top-end gasket kit. PS, If the something is "catching, while turning the crank, I wouldn't force it.

[Huron52]

Snow

If you where following the thread that was started by Marty I had my cam chain tensioner loosen up on me tracked it to a stripped screw on the adjuster. That I replaced and it quieten down (back to normal) Until saturday night!

Skids

When it happened I removed the timing side cover and tried to hand (with a wrench) turn the bike over to get to the "C" mark and it would not do that. turn that is.... Something is stopping it from turning. I think a bent valve stem hitting the piston top.
I am not going to force it.

thanks

[Snow]

Huron,
Sorry, I didn't realize you were one in the same. I need a coffee. I would tend to agree with your conclusion about valve(s) hitting. I know you can get at least Vesrah valves through Dennis Kirk (or your local shop) that ought to work.

[Geezer]

Quite often the piston will survive an impact with the valves but the much hotter valves with bend and there goes the compression. It doesn't take much of a bend either to loose compression. Often a bent valve will look good to the naked eye but when you check it with a dial indicator, the run out will be obvious.

Get some new valves and have a reputable high performance shop recut the seats. I cannot recommend lapping in valves with out cutting the seats first. The contact area shouldn't be much more than a millimeter wide (.039") or the valve won't seal properly. If it doesn’t seal, you'll be back in there doing it right long before you should. Lapping valves in without the proper machine work is one of the most common redneck bubba fixes and should be avoided in all but the most dire emergencies.


Geezer

[TopCatGr58]

"Barer" of bad news!

Hey there Tom,

Sorry to hear about your engine. After you pull the head off(since you'll need to pull the cams), you can then rotate the crankshaft with immunity and inspect the cylinder walls for scoring or other signs of impact. But, yes, if you do have damage to the pistons and such, the big bore isn't the only way to resurrect it. If your pistons are in good shape, but have excessive wear in your cylinders, you could buy new sleeves, and get them bored to the OEM pistons, get a new set of rings and rebuild it that way!! It sounds like you may have jumped a cam tooth, which put them out of time and allowed the piston(s) to make contact. Hopefully with only starting it and not running at speed when it happened may keep the total amount of damage to a minimum!? And even though you may put a big bore kit in it, you may not necessarily need to rejet, if you keep your stock breather and pipes. Mine ran great with the OEM main jets, and I was running it lean with Indy Filters and 4-1 pipes, so that's why I finally went a few sizes on my mains!

I bought the 3 valves I got for mine from Yamaha, at over $30.00 each!!!! DK only lists the intakes for 80-81 models in their catalog, no exhaust, but at $14.99. You can still get guides from Yamaha...I recently read a thread about a guy that just replaced his. That should be all you should need to replace, aside from possibly the shims for the valves you have to replace. You're going to need to inpect your cam chain adjuster, you might need to replace your chain, but you'll need to find out what caused this, otherwise, it might happen again if you don't fix it!? Good Luck.

And, Geezer, I guess you can call me "BUBBA", cause when I did my rebuild, I only lapped them, and that was with replacing 3 of them, and it still seems to be running fine after 3 rallies in 2 years. I made sure I got at least a 1mm contact line on the valve and the seat when I did them. If I've got a good seal, and proper clearance, then what can happen to the seal if I only lapped them instead of getting them GROUND?

[strom]

I replaced 2 of my valves. They werent hitting the piston, but eachother. Weird. Well, I got em from my yamaha dealer, just got me a new set of valve oil seals and o-rings that go under the valve guides. Now I don't know how to remove the valve guides.

LP

[Ken Talbot]

Strom - the manual says you need to heat the head to 100 degrees C (212 F), then drive the old guide out and the new one in with a shouldered punch. As I understand it, this is called heat shrink fitting

[strom]

Dunno if I can fit the whole head in the oven. Will try. How bout that blowdirer looking thingie that is used to heat things up? Id rather not use it due to possible head warping...

LP

[Geezer]

If the guides aren't cracked for the impact, odds are you won't need to replace them. I'd measure them with a telescoping guage to checl for belling but if they're OK, why change'em?

Geezer