Bump.

Starting a seperate category for those who have done TM## swaps.

I myself have a TM28. Damn thing will idle great, until its ridden. Once it cools it will idle again.. possible vacuum leak?

Everyone who's swapped their carbs, please post something like I have, in hopes to dial in jetting..

Current Setup:
Wiseco 10.25:1 Piston
Hot Cams Stg. 1 Cam
Mikuni TM28 Carb
Stock Exhaust
Uni 2-stage filter in CLOSED air box.

Current Jetting:
28mm flat slide
250 main
5dp39 needle
17.5 pilot
2.5 slide cutaway (its written on the top of the slide)
1.8 air jet (in the intake mouth of the carb)

Running condition: Idles perfect, as soon as its trail ridden, low-medium-high variable loads, if I try to idle afterwards it wants to bog out and shut off. If it cools for 5 minutes it will start right up. Otherwise a 1/8 throttle blip & kick is needed to get it running..most of the time.

Has a minor dead spot right off idle if its whacked open fast. When ridden its not there.

Valves do need to be adjusted again, the tappets may have loosened up.

Motor runs hot after its ridden! I think I may go richer on the main or move up a couple clips, and consider a D8 (1 step colder) ngk plug.

 

I'll post the rest of my specs later, but I just finished measuring my needle with a micrometer accurate to the 1/10,000.

I got 2.5298, 2.5150, 2.2949, 1.8110, 1.2220 and sudco has one called 5L1 and it specs out at 2.518, 2.518, 2.330, 1.811, 1.297

So, I'm close. My needle says 5HN31. Sudco dont list that number.... That's why I have to measure everything out and I was lucky to find a match. Its just as I thought too... I have almost the richest needle on the list. see http://www.sudco.com/vol33/57-59.pdf


So, I'm going to order another 5L1 and a 5J6 to try out. The 5L1 I have is kinda wore out. Keep in mind my plug looks excellent, in case you think I'm way too rich already.

The needle that comes with the 28mm carbs is a 5DP39. The specs are 2.512, 2.512, 2.440, 2.259, 1.580. Easy to see how much leaner it is than the 5L1 I'm using. Lay the 2 needles side-by-side and its very obvious that the 5DP39 on its richest clip position is still not nearly as rich as the 5L1 on its leanest!!!!

** Those numbers are the diameter of the needle in mm measured at 10,20,30,40,50mm down the needle. Its a sucky job to do,,, measuring all those points on both needles,,, I hope somebody benefits.

 

As I've said before, I think the needle that comes with the TM28 is junk for a little 230 engine. Here's a couple pics to illustrate my point.




The top most needles are the leanest,,, richer toward the bottom. Both the 220 and 230 run better with the richer needles,,, especially in larger carbs because the vacuum is lower in those carbs.