Why so slow

Wizard

Wizard

Member
Joined
Jan 31, 2013
Messages
98
Age
56
Location
Traverse City, Michigan
New to me '96 VMax 600XT; 4200 miles. Ran awesome when I bought it and for a couple weeks after, but after a long ride 2 weeks ago, it will only get up to 55 or 60 and 7000 rpms. I've changed the plugs a couple times just to be sure that has nothing to do with it. I've also thoroughly cleaned both carbs, set the float levels and idle screws, and I've worked with the primary clutch (even swapped it out with another that works perfect on a buddies VMax and mine works right on his). All I can think of is that there's a problem with something like a high speed ignition coil. Is that a feasible idea; could that explain why this thing won't wind up to where it did before? And if so, since I have no manual, how do I test for this before tearing it down?
 
Ok, it's not the secondary. Everything looks and functions perfectly on that. Switched it with wifeys SRX600 and the symptoms stay with the VMAX; both secondaries work perfectly on the SRX.

With the VMax on a stand, the motor will simply only get up to 7000 RPMs according to it's own tach which likely is showing high like they all do. The speedo only reaches 70MPH on the stand; exact same motor and track speed at half throttle as at full. It will only go to 60 tops riding it on hard packed; snaps off the line normal and climbs to 50'ish like it should, then it falls flat.

Seriously, VMax guys, does anyone reading this have any info for me so I can trouble shoot the CDI and/or high speed ignition coil (assuming it has one like my 85 VMax did) to diagnose what's wrong. I really don't want to chase after a bad hunch. I need good electrical info on this snowmobile...please!
 
The 1996 Vmax ignition coil is mounted to the airbox on the clutch side of the sled. The only other coils in the ignition system are the stator and the pickup coil mounted above the flywheel. Not sure what you mean by high speed coil as I've never heard that terminology, but all of these coils need to work at all speeds, else the sled doesn't start or run. You could check your spark plug caps as they are known to fail or degrade, they should be 5,000 ohms resistance. Is your buddy's Vmax a twin cylinder? If so his ignition coil is likely the same, you could swap it to your sled.

Are you absolutely positive that your carb slides are both still opening completely? It's rare, but sometimes the lockdown screw on the slide lever comes loose (under the top cap) on one carb. While you're at it, are both slides open the same amount when the throttle is at closed/idle position, and do both slides open the same amount as throttle is increased. That said, are you sure you are getting full opening of the slides with the handlebar lever pinned?

Any chance there is an air restriction in the airbox, or better yet in the exhaust, like a baffle come loose and is restricting flow?
 
Yeah, ok, I'm not talking about the coils going to the plugs. My '85 V-max had 3 wire wound coils under the flywheel (so, yeah, the stator); one for lighting and two for ignition. A medium thick wired one (not as heavy as the lighting coil) for low speed (up to 5k RPMs maybe, idk) and a smaller coil wound tighter with smaller wires that the CDI transitioned to as the RPMs went higher. That's what I want to diagnose, but I have no idea what color wires go where on this sled.

As for the carbs, when I had them out I removed the allen head screws that allow the needles to come out and raised the clip (dropped the needle) in hopes leaning it out a little would help. It did make it snappier, but the mileage is still shitty; I got 55 miles on 8 gallons over the weekend which seems really bad, imho. Anyway, throughout the process, I found nothing that seemed off, both slides rested in the same idle position and both rose all the way up as the linkage cam (where the throttle cable goes) was rotated. On reassembly I absolutely made sure I had a little slack when the throttle isn't being pushed and the cam rotates all the way when I push full throttle. I could maybe still slip a piece of paper between the throttle lever and the grip.

Compression is at 145 to 150 on both cylinders. The airbox was dirty as were the intake side of the carbs coming out of the air box boots, but I cleaned everything up like brand new. Unless I missed something in the cabs where maybe they sucked in some dirt, idk. Both main jets were clear, but maybe I missed something else. I guess I'll go through them again and also make sure neither of them are slipping under the top caps and I'll pull the exhaust and see what's up. But to hit the exact same RPM whether on a stand or ripping down the trail seems a bit odd to me; I wouldn't think blockage would give such consistent and predictable/repeatable results.
 
Tore it down, put it back together. Exhaust blockage is not it, the thing looks new and breathes easy, clutching's not it, carbs came apart and went back together perfect in terms of clean open jets, float level is in spec, float plungers are shutting fuel off as they should, the slides go all the way up for WOT, choke functions perfectly, I pulled the reeds and there's nothing wrong there, looked at the pistons through the reed cage void when they were out and all's well, compression is great, I cleaned the fly wheel off just in case and tried a known good main coil so the plug boots aren't the culprit. Got done and it's exactly the same. EXACTLY!!! The only thing new I've discovered is that if I only give it about 1/3 throttle while going down the trail on hard packed, it will accelerate past 7k to 8k and about 70mph, maybe more, but if I squeeze the throttle more, it comes back down to 7k rpm almost as if it's getting too much gas; too big of main jets (?), idk. Basically, I think I'll tie a rope to it and use it for my boat in the summer. I'm getting another SRX cuz this things a POS!
 
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I know if you become a VIP member, someone will send you a link to a manual. I have one, but it is not on my home PC. I had an old Ditch Pickle that was slow until I changed the stator, then it got fast. But I can not remember the specs on it now.
 
Reposition you needle clip to the middle. You could also be running lean at WOT. This will give the same scenerior as you are mentioning. Is the Main jet same as oem specs? Good luck Al
 
Messed with clutching some more to no avail so I decided it must be down to the CDI, the carbs (which I was going to swap out because I thought I'd got the ones on it right) or the main coil going to the plugs even though I'd swapped that with one I thought was good. I guess it wasn't because I pulled the one from my '85 VMax (which is getting closer every week to being nothing but a parts sled - Lol!) and of all the things I've done so far, this was the one I thought wouldn't make any difference...but holy smokes was I wrong because now she hits 8300 RPM and rockets to 80 in an 8th mile! Love it! Problem solved. Thanks for all the help!!!
 
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