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Recommend Mod's for 1989 RM250

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Hi,

Have my RM250 running good but see that most put a FMF Fatty Gold series pipe and Boyesen Pro Series Reeds on their bike. Will I see/feel much difference with the pipe and reeds???

Currently the bike is bone stock except for the sprocket ratio. I ride woods and trails/Hare scrambles.  

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The pipe, reeds and silencer will make a noticeable difference.  Beyond that a flywheel weight would be a good idea, it'll help your bike hookup better.  My personal recommendations will depend on where and how you ride, but here goes:  A 6 ounce would be fine, an 8 ounce if you normally rode 4 strokes and the 10 ounce if you ride in really slick conditions.

https://www.steahlyoffroad.com/suzuki-rm-250-89-93-flywheel-weight-705

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Installed the fatty pipe and pro series reeds, didn't seem to make much difference. Maybe a little off the bottom end and maybe a bit more in the middle, maybe. I haven't rejetted yet but parts are on order to play around with. The current jetting is a 370 main, 50 pilot, 6AEJ1-62 needle, clip in top position, and air screw out 2 full turns. Run 50:1 premix and live in Indiana (800 ft sea level). I've never jetted a carb before and was wondering how much difference changing one step/size will make. I played around and moved the clip on the needle to the 3rd/middle position. Bad mistake, ran very rich and sounded blubbery. Was surprised moving clip would make such a difference. I've ordered a 360 main, 45 pilot and a 6AEJ1-63 needle. From the needle position and the air screw adjustment it seems carb needs to be leaned out a bit with the new parts. Bike seems to run pretty good but I seem to always want more or be assured it's running it's best. Question......When making jetting changes is there much of a range or will small changes make big difference??? Should one try to run a bit lean or a bit rich??? My plan is to install the 45 pilot and 360 main, set air screw and take a test ride. Then install needle with clip in the 3rd/middle position. Test ride again doing the chop test, bought several plugs for testing. Any better approach????

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Kind of hard to understand why you didn't feel much of a difference after installing the pipe and reeds.  What silencer is on the bike?

Doing jetting chop tests are tricky, you need to clutch and kill the engine as quickly as possible, which can also be dangerous.  And then you really need to know how to read plugs, plus the engine needs to be warm before you start and then the oil in your premix can skew the results if you don't know how to read beyond the un-burnt oil.  This is why most people just go off of feel when jetting.

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Think silencer is a pro circuit, think. What is dangerous about clutching and killing engine?????? Hoping to get jets and needle by Friday to play with,,,,, race on Saturday.

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Received the new jets and needle but after lots of reading decided to go with 32:1 premix instead of the 50:1 in the past. Filled the tank then adjusted air screw to 1 1/4 out from fully seated (was set to 2 full turns out before). Took bike for a short ride to warm up and see what difference with just the premix change. Bike ran pretty good but would pull down a bit when I let off the throttle and coasted. Moved the needle clip down to the second groove from the top and that fixed the issue (was in the top groove before). Was surprised changing the premix ratio would make that much difference. Ran out of time and didn't play around with jetting due to a Hare scramble the next day. Bike ran great and I think the Fatty pipe and reeds did make a difference. Things went great until  float issues started and caused me to drop out. Ordered a new float needle valve assy which should fix that problem. Will play around maybe with the main jet and drop the clip one more just to see what happens but for now I'm good with the bike.

Have a great day,

Bob

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