Trailmaster help needed

[Mg1978]

New here,
We have a Trailmaster 150 XRS. Couple months ago it started smoking terribly. Long story short the piston was toast. After replacing with the rebuild kit I found the carburetor was full of old gas as well. Figured while I had it apart might as well get an aftermarket carb. Opted for the Mikuni VM26-606. Got everything back together and have tried different combinations of pilot and main jets. I started with the 145 main and 17.5 pilot. Went all the way up to 185 and 22.5. It will start and run but no where near the speed it was. When in neutral the engine does rev higher than in drive. Seems like there isn't any power though. Forgive the rambling. Wandering if there are any things I need to try next. I currently still have the stock intake and exhaust. Also the CVT is stock.

Any suggestions?

[SYCARMS]

Since you mentioned the speed is down with new carb as compared to old carb I would think it is in the carb. What color is the carb, any smoke on acceleration, any stumbles and if so where. This is to be done first in neutral then while driving. The people I know who went with that carb including myself had to raise the intake for the carb to fit due to it being longer than stock CV carb.

[ckau]

Have you looked at the fuel supply? larger carbs need more fuel. The stock fuel lines were just adequate to supply A 24MM. Your going that far up in jetting can indicate compensation for lack of fuel. A lack of speed can result from not enough fuel supply for the carb to operate at full potential.

[Mg1978]

I'll check that this afternoon. I'm using the stock vaccum valve, maybe I should swap to the manual one

[SYCARMS]

Karl from the other forum is using the VM26 606 on his buggy with a 62mm slug, 4 valve head and 2mm stroke and still has the vacume pump with 3/16" lines. These carbs have to be tuned to a specific engine. Unlike the CV carb in which jetting is the tuning. The VM series besides jetting you have needle jet, jet needle, needle and seat as well the slide to consider in tuning. The fact that your engine is still stock it will not require any more fuel using the slide versus the CV carb. Google tuning the mikuni vm series carb. I had referenced < Mikuni carburetor operation and tuning > by Ian Williams Tuning.

[wildbob]

I fought with my vm26-606 for months.. I was at the point of putting the CV carb back on. I could not get it to jet correctly or work well at all. It turned out I had several problems working together to make jetting a nightmare. Firstly, my tank wasn't venting so it would vacuum lock, my coil wire had broken and would intermittently stop conducting, i had a tear in the connector from the intake to the carb, and lastly, I had the carb apart and I bumped into the table, I noticed as I sent the needle rolling that it was warped causing the slide to not operate correctly. Luckily, I had a spare vm26-606 (because I had too many adult beverages one night and forgot that I already ordered one). I fixed the issues and last time I drove it, it was blasting around like never before. Then since it was running better than ever, I tore the motor apart for my new build..

[SYCARMS]

Just to illustrate the difference in the 2 carbs. On my 150 stroker motor, after installing the custom cam I needed a larger carb and went with the KEIN 32mm Pumper CV carb. I had to rejet it naturally. I then took the plung and went with a Mikuni VM 32mm slide carb and the engine would not run, it was just dumping fuel. Jetting was not much help. I ended up having to change out the needle jet and jet needle as well as the throttle valve. Once I had this correct I then was able to jet it to where it run like a raped ape but at top end it was leaning out to the point the plug was white with metallic speckles which was from the piston melting. I than had to run a larger needle and seat for more fuel to the bowl. Keep in mind these were both 32mm carbs. Slide carbs are superior to the cv carbs but the same mm slide carb will fit more applications than a cv carb. Once you get them tuned you will never go back to the cv carb.