Vintage Dirt Bike Q & A

Ive been looking at the MT250 carb and wondering why everything i read says its the only one that fits on the bike and im stuck with it... Ok, so its an older 28mm carb and anything larger wont fit the manifold of course, so I was looking through my stash of carbs for my RD/RZs as they are 28s too and wondering if a more modern carb would help the little MT a bit? I can make both the PWK28 (in this case from a KR1S) or the standard RZ carb which is a mikuni fit the manifold, but both need a longer boot from the airfilter, which is fine. But, will either of these be better than the original or would i be wasting my time do you think? The PWK is a way better carb on the RZ motor than the standard carb as it smooths out the powerband and avoids a stumble when the Power valve opens (not an issue here naturally), so even staying with the same size you can improve running and torque etc... Ok, yes I know that deep down i will want to go for the CR top end eventually, but i was hoping for a little extra pep since i have to rebuild a carb either way... any thoughts guys?

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MT250 with CR250 top end & Bassani pipe... almost fully restored.

See more of my motorbike builds at my Honda MT250 and Yamaha RD and RZ website, 2Smoked.com

If you like watches, check out my websites: DeskDivers.com & PloProf.com

I have a 32mm Mikuni flat-slide on my MT. I managed to stretch the original manifold around it. I then used some heat shrink tubing intended for a 600V line as the tube from the carb to the original airbox.

Check out my post below titled "Performance Mods For An MT250?"

I have since changed out the airbox/battery box for an open oiled foam element type of filter. The MT intake manifold & port are the choke point & a larger carb can only do so much.

~JM~

PS. I have a cylinder head temperature guage installed to monitor how hot my engine runs under load, etc. I'd be leary of messing with carbs without it.

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Thanks for posting, its much appreciated. Food for thought....

I found the thread you mention and enclose it here for completeness, its worth reading as you say.
viewtopic.php?t=2943

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MT250 with CR250 top end & Bassani pipe... almost fully restored.

See more of my motorbike builds at my Honda MT250 and Yamaha RD and RZ website, 2Smoked.com

If you like watches, check out my websites: DeskDivers.com & PloProf.com