Vintage Dirt Bike Q & A

I've been collecting parts and pieces for an 82 CR250 I had acquired last year.
Getting things in place I have finally gotten to test run it.
Cold it starts fine using choke, usually 3rd kick.
After 15 seconds or so I close the choke and it continues to run and warm up.
Clicking into gear and slipping the clutch it fires normally and I easily drive off.
However, when I open the throttle to run through the gears, it produces a very rough chop and fails to wind up like it should...
I've had the reeds out and cleaned. They are in good condition and lay flat against the housing.
I suspect the main needle may be the culprit. My next guess would be to move it down to the next clip grove.

If you have an idea, please let me know..

Thanks!
Dave

Your main could be dirty as you suggested - but that's pretty obvious. Pull the mainjet and see if you can see through it. Also jump onto a parts fiche and see what size main comes in the bike and compare it to what you have to make sure nobody put anything odd in your bike... On the needle it's a safe bet to start in the "middle" so that you can test your bike and get it running close before fine tuning it.

Another thing you will want to check is the float level - has that been set? The best way to "eyeball" it is to take the carb and hold it in your hand while on it's side so that the floats are hanging down towards the ground - slowly tip it so that the floatbowl is going upward and watch the floats gently move. When you see them touch the float valve/needle the floats should be not quite parallel to the gasket surface of the carb - just below that so that they aren't level with one another... Yours might be too low.

Then there is the biggy - don't have enough info - but it could be your stator messing up too. Try those carb checks first though...

Anyone else have any ideas?

Peace...
Mikeee P

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The Race Isn't Over Until YOU Cross The Finish Line!

Ignition maybe, yep.

But, an over-oiled air filter or a rag left in the airbox behind the filter could be sneaky problems causing too rich of a condition at large throttle openings. Does it rev okay without any load? Have you kept it wide open through all the gears to clean in out? It might just be loaded up.

That's my 11:00 at night obvious checking points. Good luck!

No air filter in the box. Attempted to clean it and it fell to pieces.. A new filter is on order.
The problem occurs even in neutral with no load. Throttle is smooth and responsive up until a point.
A neighbor suggested that the muffler may be fouled and causing the problem. I plan to remove it to see if it may be causing the issue.
I have an origional 82 carb that I have yet to try too. I'm pretty certain one of these two potentials will correct my issue. I'll post and let you know when I try them what the outcome is...
Thanks for the suggestions!
Dave

Dave,

Another thing you could check is the air jet and its passage to the needle jet. If this is dirty or clogged, the bike can run richer and richer with increasing vacuum (rpm) above 1/2 throttle.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric

Sadly I had the bowl off the carb and failed to check to see if the jets were clear. It would be a simpler problem to solve than the silencer...
I have the next two weeks off and plan to figure this out,..weather permitting.
Thanks for the suggestions!
Dave