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90 rm250z bogs at almost all throttle positions

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Hey my buddy has a 90 rmz250. He bought it about 9 months ago and it hasn't ran right since. When he got it you would ride it and anywhere below 3/4 throttle was great but from 3/4 on up it just bogs. Bogs so bad it loses speed fast. He took it to a shop and they told him the replaced the crank base gasket and put in a fatter main. Got it home and now its the opposite below 3/4 it bogs and above it runs like a raped ape. Can some one help me with what the jetting should be? Or any other ideas? The elevation here is about 4000 feet temp in the 70 to 110 range during riding season

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a 90 RMZ 250 ? I didn't think they made them in 1990. If it is an RM 250 two stroke, try cleaning the carb and re-jetting. Follow the FAQ at the top of the forum. But it probably needs a rebuild first.

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Sorry it "says" its an rmz. I don't know much bout suzukis I'm a yammie guy. It is a 2 stroke rm set up for trail riding

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Sorry it "says" its an rmz. I don't know much bout suzukis I'm a yammie guy. It is a 2 stroke rm set up for trail riding

Do you mean RMX?

Post a pic please....

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It must be an RMX.

On a bike that old the first thing I'd do it install a fresh top end. There's no telling how many hours are on the current one. Check the reeds, clean the exhaust valves and check to make sure the exhaust valves are working while you're in there.

Once that's done, then start with the tuning. Assuming it still has the OEM carb and no other mods, the factory settings are #230 main, #45 pilot, air screw two turns out, needle clip in the 3rd position, float height 16mm. Any adjustments will depend on your altitude and any other mods to the bike (pipe, reeds, etc.) As above, the FAQs section has a good tuning guide.

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Thanks for the numbers. That what I needed. It is supposed to be a new top end (jug gasket looks newer) I just wanted to start at stock jetting and go from there

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