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| MT250 Base Jets https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=3814 |
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| Author: | mbilder [ Fri Sep 28, 2012 12:30 pm ] |
| Post subject: | MT250 Base Jets |
I have a November 1974 MT250 and the throttle response is less than good. Now that I have rebuilt two MR175s, I think I should expect a little more from my MT250. It putters on the idle to 1/2 throttle and does not snap to or snap back when the throttle is revved. I want to check the jetting to see if anything has been changed by the previous owners. I checked the timing with a timing light and it appears to be pretty close to the mark. Does anyone have the standard jetting for me to compare? |
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| Author: | rayivers [ Fri Sep 28, 2012 3:58 pm ] |
| Post subject: | Re: MT250 Base Jets |
122 main jet, 60 pilot, 3.0 throttle slide, 271002 needle. Ray |
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| Author: | 4x4_Welder [ Fri Sep 28, 2012 10:50 pm ] |
| Post subject: | Re: MT250 Base Jets |
To save you a ton of time and tail chasing, change the needle jet. Mine was worn, and it would not idle and was uncontrollably pig rich below 1/2 throttle. I changed the needle jet out for one from my parts carb, and it is far better. New ones are available, but only from a supplier in the UK for 25 Euros plus shipping. I am working on putting a Mikuni on mine, since I have a torn boot anyways. I am having to make a new mount for it, but that's easy. |
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| Author: | mbilder [ Sat Sep 29, 2012 7:47 am ] |
| Post subject: | Re: MT250 Base Jets |
I wanted to check to see what was original first, because I know at least one "carb kit" was used on it and I don't know what jets were replaced. It had it bored one over and never changed anything, so I figured I would start with the baseline before making any jettting changes. Any suggestions on what I should expect to change in an overbore? Any reason for going with the mikuni? I have one of those sitting around too. |
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| Author: | 4x4_Welder [ Sat Sep 29, 2012 11:20 pm ] |
| Post subject: | Re: MT250 Base Jets |
I'm going with the Mikuni for three reasons: It's larger, parts are more readily available, and I am more familiar with them. As a plus, they do seem to respond to tuning better than the Keihins. I found a carb mount to go to a tube, so I'm having a flange cut, then just weld a tube to it and clamp everything together. I still haven't decided if I will put an oil port on it or run pre-mix. There's a lot of hills around here, so I may stick with injection. |
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| Author: | scouter99 [ Thu Oct 25, 2012 5:56 pm ] |
| Post subject: | Re: MT250 Base Jets |
I'm wanting to put a Mikuni on mine also i am sick of messing with the Keihin. What size of carb are you using? Any jetting recommendations yet? |
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