1982 XR250R cam and balancer timing.

[juniordragster123]

Hey guy's I'm rebuilding a 1982 XR250R engine and the crankshaft has been all pressed apart including the balancer gear and the cam chain gear. I notice on the cam gear and the balancer gear there is no spline or key, Just a press fit. There's no dimples on the crank and gear's or anything just one mark on the balancer itself. So how would I know where to press these gear's back on in the right location. Ohh if it helps on the camshaft big gear there are 2 marks on it. Thanks hope somone can help me.

 

[juniordragster123]

C'mon 7 views and no replies? I hope I have come to the right place for help.

 

[Patman]

I'd suggest checking with the local Honda shop. A factory service manual would be very helpful for this type of thing but I don't know if they are still available.

 

[juniordragster123]

Would they go into detail like timing though?

 

[Ol'89r]

C'mon 7 views and no replies? I hope I have come to the right place for help.

Oops. Sorry! Hope we haven't wasted too much of your time. :whoa:

When installing the crank, place the counterbalancer in the cases and align the crank so that the counterweights, (heavy end of both the crank and counterbalancer) are EXACTLY opposite or pointing away from one another.

We'll try to be more punctual next time. :fft:

 

[juniordragster123]

So basically when the piston is going down the balancer counterweights go up to counter act all the rotational mass and balance it all out?

 

[Ol'89r]

So basically when the piston is going down the balancer counterweights go up to counter act all the rotational mass and balance it all out?

Exactly. :cool:

 

[juniordragster123]

Thanks alot! I cant wait to get this bike running. What about the location of the camshaft timing gear and where it gets pressed on?

 

[Ol'89r]

Thanks alot! I cant wait to get this bike running. What about the location of the camshaft timing gear and where it gets pressed on?

The camshaft timing gear is bolted on not pressed on . When you bolt it on to the camshaft, make sure the marks are facing out. When you time the camshaft, put the piston on tdc and make sure the lobes of the cam are pointing down towards the piston. Line up the two scribe marks on the camshaft sprocket so they are parallel with the gasket surface on top of the head. Check again to see that you are on tdc and then tighten the bolts on the sprocket. It's a good idea IMO to use blue Locktite on the sprocket bolts.

 

[juniordragster123]

I mean the 15 or so tooth that gets pressed onto the crankshaft that drives the cam chain inturn driving the camshaft. That just gets pressed on whereever then you time the cam like you said?

 

[Ol'89r]

I mean the 15 or so tooth that gets pressed onto the crankshaft that drives the cam chain inturn driving the camshaft. That just gets pressed on whereever then you time the cam like you said?

The small camchain gear on the crankshaft should be splined and indexed and will only fit on one way.

If for some reason your gear is not indexed, then you will have to time your cam the old fashioned way. With a degree wheel and dial indicator.

 

[juniordragster123]

Theres no spline at all. Just a gets pressed on. Why cant I just figure out where to press it on and press it on and just make sure its at TDC and make sure the two cam scribes line are level with the gasket surface?

 

[Patman]

Sure you CAN do that, you can do anything you want but I would suggest following 89'ers advice because he already made it clear what you would need to do if the gear was not indexed.

Just as a suggestion, next time you decide to take something apart look at it, take picutes and if it appears it may be difficult to get back together exactly correct mark the two items. I would have been inclined to put a little drill / punch mark or scribe mark on them. Hind sight being 20/20 I'm sure you would have as well but you didn't so now you have to old school it.

 

[Ol'89r]

Theres no spline at all. Just a gets pressed on. Why cant I just figure out where to press it on and press it on and just make sure its at TDC and make sure the two cam scribes line are level with the gasket surface?

Yes you can do that. That would be a real shot in the dark. And there is a small chance that you will get it close. But, there is a bigger chance that you will be off several degrees.

We are talking crankshaft degrees here. Your cam has to be timed within a few crankshaft degrees for it to run correctly and for the valves to clear your piston. If the cam is off too many crankshaft degrees, your bike will run like crap or not at all and you are taking a good chance of destroying your top end if the valves hit the piston.

The correct way to do it is to use the proper valve opening and closing specs out of the service manual and time the cam using a degree wheel and dial indicator. Any other way is just guesswork.

If you do decide to do it your way, it would be advisable to clay the top end and make sure the valves are clearing the piston before you try to start the engine. It's a lot more work to clay the top end than it is to degree in the cam but, suit yourself.

Some of the parts for these engines are getting hard to find. I suggest you do it the right way or you could have a bike that you can't fix.

Sorry if that's not the answer you're looking for but it's the only one I got.

 

[juniordragster123]

Dude, I didnt take this apart some other guy did about 8 years ago did so you cant tell me I wasnt inclined enough to mark them first. This isnt new to me as I drive a alcohol dragster and I know what your saying and I have somone that can help me degree in the cam.

 

[Patman]

Dude, I didnt take this apart some other guy did about 8 years ago did so you cant tell me I wasnt inclined enough to mark them first.

A thousand pardons.

This isnt new to me as I drive a alcohol dragster

What has that got to do with ANYTHING? :laugh: I slept at a Holiday Inn Express a few times and they still won't let me do Rocket Surgery. :whoa:

..and I know what your saying and I have somone that can help me degree in the cam.

So then why the big fuss about "isn't there another way"?

 

[Patman]

Which part number?
http://www.bikebandit.com/houseofmotorcycles/showschematic/m3058sch5570

 

[juniordragster123]

A thousand pardons.

What has that got to do with ANYTHING? :laugh: I slept at a Holiday Inn Express a few times and they still won't let me do Rocket Surgery. :whoa:

So then why the big fuss about "isn't there another way"?

It's pretty irelevant to dirtbikes. I was just trying to say I'm not totally new to mechanics and general work and that I understand what your saying when you use words like BDC TDC and other stuff like that. Thanks for the help Sorry to waste your time.

 

[Ol'89r]

Hey juniordragracer.

What kind of engines do your guys run in your junior drag racers?

 

[juniordragster123]

I hope your not asking me this just to say "Told ya so thats no irelevant" But we run billet flat head engines. Makes around 70 HP at 9000 RPM. Pushes my Outlaw dragster 90 MPH in 7 seconds. It'd give most of your dirtbikes a run.

[URL=http://s284.photobucket.com/albums/ll33/juniordragster123/?action=view&current=MOV02503.flv]

 

[Ol'89r]

Which one is the dragster, the green one or the silver one? :whoa: They both use the same engine don't they? :laugh:

No worries juniordragracer. I'm just messin' with ya. ;)

The reason I asked is because I have a friend that races carts and I believe they use the same engine in the B&S class. Definitely not your grandfathers Briggs and Stratton.

Very cool lookin' car. :cool: Bet it's fun to drive.

 

[juniordragster123]

Thanks man, Yeah seems like you understand a bit. The engines have to appear to be 5 hp briggs STYLE. But this engine is just wild. Its blueprinted and MUCH larger than a briggs 5 HP. I tried to post a video. I'll try again after work Cya.