Hay, need a little help with a 92 trail 488, friend just bought it with only 4000 miles,like new.It starts and runs great but after about a hour it starts to bog in midrange.If you get it up too full trottle its ok.Checked engine and compression was down.Replaced top end compression is now perfect.Went for a ride and after an hour bog returns again.We found a needle jet bent . We replaced the needles and jet needles or brass as some call them, carbs are spotless now but were pretty gumed up, sled still does the same thing. Could crank seals be doing this? It only does it after it is warmed up and seems worse when it is warmer . The bog is around haulf trottle Help please!

If the air temps are above 30 degrees F, and you are running stock mains you need to rejet, or replace your secondary spring to start.

Hay dave thanks for the info,both clutches have been cleaned and the stock driven spring red has been replaced with a new silver.If the mains are too fat would this cause the bog in the midrange ? When we cleaned the carbs they were really gumed up and we cannot see the jet number on the mains.My friend found out this sled was burned down before.Maybe the origional owner put in larger mains to help save the motor.Stock calls for 230, what do you recommend for around 0 c or 36f thanks alot!

I would put 210 jets in for that temp, however your main is not the problem, does'nt kick in till 3/4 throttle. I would also put the clip on the jet nedle 1 down from the top, thats your mid range bog. I'm a little surprized its taking that long to bog down, possibly you have a cdi unit breaking down once you reach a certain temp.

Hay tc1 , put the clip in #1 made a big difference , thanks , but when the sled still warms up after about a half hour if it idled any amount it would still bog a little half trottle. I have not had a chance to change the mains. I will put in a set of 210s tomorrow, its a hundred percent better.I am going to put in a new set of primarys too. I know the mains only control the last three quaters trottle but is there a little overlap there and it is fairly warm here around 45 f so could this be the rest of the problem?

On my 87 Trail with the same style airbox as yours, I ran 210 mains and needle in # 3, down to -20. #2 on the needle can get very lean when cold. Remember a fanner uses some of the fuel for cooling also. I'd pull carbs apart again and be sure pilots are clear. A fanner will bog at 45degrees f with 230 mains. Go to 190 at that temp. You said it was it was burned dow, if someone did a hack porting job, even more reason to bog at higher temp.