Engine troubles - Snowmobile World : Your #1 Snowmobile Forum

diamondstealth · 01-02-2002, 07:16 PM

I have a 93' Storm with updated 96' Cylinders and heads. the heads are milled 25 thousandths and the cylinders have light trail porting. Problem is, I have hardly any getup and go, alot of low end bog, and hardly no top end. It maxes around 6k to 7k if im lucky. Thats about 60-70mph. We didn't change anything in the carbs, should the jetting be changed? Anybody have a good setup? It just got a new comet 108exp and a different secondary spring. We went from a real weak blue to a black (needed to ride). Any suggestions? Everything else I believe is stock. Thanks

MrSector9 · 01-04-2002, 12:43 AM

Did you check the jetting? If it is using the stock jetting then you might have already cooked the motor because it should have been changed if those mods were added.Could also be losing compression somewhere,not firing on all 3 lots of different things to check.Reply with what you have checked already and I will see what else to try.

BJ White

diamondstealth · 01-04-2002, 04:37 PM

I believe the motor is still to the stock 750 Jetting. Would you happen to know what needs to be purchased for rejetting? I cannot get an answer out of any of the 4 local dealers. If I could get some part numbers or something, that would really make my day. (440 arctic cats are beating me!!) Thanks for the help.

MrSector9 · 01-05-2002, 01:05 AM

The only things you would need to buy are new jets.The size I am not sure of that you owuld need.I would say at least 5 sizes maybe.Do you know how to properly jet the machine? start it somewhere you can get a good run.Hit the throttle wide open until then engne shifts and you reach top rpm then hit the kill switch whith the trhottle open.Check you plugs for the color on the bottom.To be safe they should be a chocolat brown.The darker they are you are too rich and need to go down in jet size,the lighter it is you need to go up in size.If it is very light be careful and dont hold the mahcine wide open until you rejet the machione because you iwll definatly melt a piston.if anyone else can add to this be welcome

BJ White

Shayne · 01-05-2002, 10:44 AM

Have you ever ran the sled with the '96 cylinders before? Were they ported when you got them? A bad port job will kill an engine's top end OR bottom end performance.

diamondstealth · 01-05-2002, 12:12 PM

Yes, they were ported when I got them, the mechanic I had put the motor together stated that they were lightly ported. As for plugs, you can barely see any color change. I can have someone change the jetting, I just need someone to tell me what to get. Thanks for the help.

ninja-plumber · 01-05-2002, 05:11 PM

I beleive the first part of your problem may be the clutching. The 96 specs call for 8250 rpms. You stated that you have changed some springs and the clutch. I know that with the updates that the sled has a fairly narrow power band. If I remember correctly it would come on somewhere just below 7 grand. I would start there first. You may have to light a primary spring or to heavy weights. The stock Polaris spring was blue with 10-62 bushed weights. The helix was 34 degree and spring in 2nd hole. The stock jetting with the updates is 380-390-420. This was up to 900' elevation and good to -20 degrees F. The Jet Needle is 6CGY3-3. The pilot jet-45. Air screw 1 turn. As I stated earlier start with your clutching. One more thing, with the shaved heads only run premium. What is your compression when cold?

diamondstealth · 01-05-2002, 07:36 PM

Ok, just went and picked up the mains and the pilots are on backorder. Let you know on the powerband/clutching after i get the jetting done. And I don't have a compression tester.

ninja-plumber · 01-06-2002, 05:38 AM

Did you check your main jets before you picked up the new ones? The 93 storm came with 390-390-410 (P-C-M). They both run the same VM38SS carburators. This is pretty close to the 96 specs. The difference between the 2 is not enough to cause your problem. Also note that the stock timing on the 93 model is 28 degrees at 3000 RPM's. The 96 updated specs call for 24 degrees at 3000 RPM's. At 8000 The 93 is suppose to operate at 12 degrees. The 96 update at 11 degrees. This tells me that if you adjust yours for 24 degrees then your 8000 rpm will be around 7 degrees.They both list a different CDI box which would have different timing at 8000 rpms. I would try turning back my current timing just a little bit, Maybe 26 or 27 degrees at 3000. The CDI box identification on my 95 with updates was CU2508. I wouldn't run right out and buy one until the last thing. Hope this info helps and doesn't add more confusion. CONFIRM YOUR CLUTCHING FIRST!

diamondstealth · 01-06-2002, 06:07 AM

I talked to the dealership, and they said the 93 750 had 330s for mains and 35s for pilots. And the 96 had 400's and 45s for pilots. This right? He got this right off his computer. Stock jetting. Thanks for the help.