Putting the head back on and I'm LOST - help?

Don /

Jan 04, 2002 06:58PM

Hey guys, I've ordered a manual but it hasn't shown up yet. I'm trying to put my 250cc honda elite engine back together but I seem to be a bit lost. Maybe you can help?

The problem is the timing I think. When I took apart the engine I marked the cam gear and then a bit later I marked the chain where I thought it lined up with the mark on the cam gear. I should have marked them together so I'd know exactly where they were before I took it apart but I didn't. Now after getting it back together I am hearing some nasty sounds in the engine like it's way off the timimg mark.

I pulled the valve cover back off and removed the cam again. I then lined the marks up and put it back together but I can tell I'm still way off.

Even if I'm off one tiny tooth it won't run right?

The cam gear has an "o" mark on it for reference I assume.

Anyone have any idea what I do to get this back together correctly?

thanks

Re: Putting the head back on and I'm LOST - help?

Ron Brown /

Jan 04, 2002 07:45PM

Don,

In most motorcycle engines, the piston and valves will hit each other if the timing is far enough off.

If you heard any noises like this, you should remove the head again and check for bent valves as they have a habit of breaking off the head and eating the engine.

If the valves did hit the piston, they will have left a mark in the piston crown.

Wait until you get a copy of the valve timing instructions for your bike and follow them religiously. A one tooth error is enough to screw it up royally.

Ron

Re: Putting the head back on and I'm LOST - help?

Don /

Jan 04, 2002 07:51PM

Here's a pic of the valve cover with lifters in it. http://communities.msn.com/_Secure/0LAAAAKsNoxH1cd8k5!cyuvOY!vBwOrStSHDKL1Zs0kxD46oCe0Ga0gQTvNftdsfHRXa7uOTPWM/P1010004.JPG

Here's a pic of the cam with the mark http://communities.msn.com/_Secure/0LABsaawNxhH1cd8k5!cyuvoOE5wjhNFa9sursE54Y7B6WbKAIfFoGftNN00SjuU3*PoGeAFH1w/P1010005.JPG

A pic of the cam from the other side http://communities.msn.com/_Secure/0LABERakNXRH1cd8k5!cyuhfAsBdyyLAK9oYm8e3jdC8PERG3h5ffAJwINAWrPG9V9kssNQPQH08/P1010002.JPG

last pic from above http://communities.msn.com/_Secure/0LAAAAKoNgBH1cd8k5!cyutpYwjyx87bg3sH1IW1rMvU44Mygr7rniUN8DiZeBGAKypjt0OnaB!g/P1010003.JPG

Re: Putting the head back on and I'm LOST - help?

Don /

Jan 04, 2002 08:59PM

Ron Unfortuantely you're right. I just pulled the head off and I've bent the intake vavle really bad and the exhaust valve also hit the piston but doesnt appear to be bent. What a dopey move ...trying to do this rebuld without a manual!

SHIT!

I just had these new valves and seals installed!

Re: Putting the head back on and I'm LOST - help?

RogNC /

Jan 04, 2002 09:59PM

Don, there should be a mark (0) or (I) on both gears the chain shouldnt matter, well not in my experience, BUT the marks only line up once at TDC,, in other words once the motor spins over the marks wont line up again...sorry you messed up the valves I bet their 40 bucks apiece or so, the seals should be ok unless you wallowed out the guides, oh it may run 1 tooth off but it would be really slow and heat up almost immediatly I had that happen on a B&S 5hp and it glowed red in about a minute (spooky) good thing it was experimental........Rog

DOH !

Fred /

Jan 04, 2002 10:59PM

You should have gone to a library and gotten a book on small engine 4 stroke repair, one with an overhead cam section might have saved you this problem...

The part you missed was that BOTH the crank and cam have to have their locater marks lined up correctly.

There is either an inspection cover on the flywheel... or you have to remove the side case to find the marks on it.

You ain't the first one.... by a long shot.

A whole lot of American hillbillies have had there asses saved a million times because American V8s with pushrods don't have overhead cams that have to be timed after only the heads have been off.

Re: DOH !

Don /

Jan 05, 2002 09:24AM

Thanks for the info guys.

Re: DOH !

Ron Brown /

Jan 05, 2002 11:03AM

Don,

Sorry to hear that.

Make sure you have the exhaust valve checked too. It would be a bummer to reassemble with a slightly bent valve.

Ron

Re: DOH !

Don /

Jan 05, 2002 05:38PM

I figured out what happened. When I took this engine apart I marked the cam and the chain where they went together. I would not be turning the engine over at all. That way I could put it back together exactly at the same timing spot. Sounds good right? Well if I had kept constant tension on the cam chain my idea would have worked. But I tied a wire around the chain and let it droop down in its slot. What I didn't realize is that it came off its sprocket in the case! I put the cam back in and put the chain on the cam with the marks lined up thinking I was good to go but the chain did not go back on the lower sprocket exactly where it had came off!

Duh!

I figured this out because today I looked down through the hole in the side of the cylinder into the case and noticed the cam chain was off its sprocket. The only way I could get it back on was to remove the cylinder ...which I was hoping I wouldn't have to do. Now that I have the cylinder off I figure I might as well have it bored .0020 over and get a new piston, rings, wrist pin and clips. That'll give me a completely new top end.

I called Helminc and my manual is on its way ...I'm gonna need it! :)

Re: DOH !

Jamie /

Jan 06, 2002 03:08AM

Experience comes from mistakes. Knowledge comes from experience. In order to have the latter, you must have lived through the mistakes.

I noticed someone mentioned a Briggs engine, I had a similar experience with a rebuild on an amost brand new engine. The result was a blown motor. "litarally, I got it to run for about 1 minute (like crap) and then I had a hole in the engine case."

You have more guts than most taking on the rebuild that you are working on (when you get the manual, your going to sa stuff like "Damn, I should have known that" and "That is a whole lot easier than the way I did it!")

Be patient and wait for the manual. It has specs and stuff that you really need to make your scoot the performance monster that you want it to be.

Jamie

Re: DOH !

Don /

Jan 06, 2002 11:32AM

agreed jamie

MOPED ARMY

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