Viper only getting 8000 RPM's

superfan75

superfan75

New member
Joined
Jan 17, 2013
Messages
180
Age
50
Location
Topsham Vermont
I know there have been some posts on here about not getting top RPM. My Viper only will run up to 8000 RPM, even with it on a stand. I have cleaned the carbs and cleaned and adjusted the PV's. I checked the wiring harness and protected it with wire loom protector. I didn't see any rub throughs in the wiring harness. The machine starts and runs pretty good and has a full tank of fresh ethanol free gas. It has new plugs and it looks like it has good spark in all three cylinders and there are no warning lights lit up. I was thinking of pulling the reeds since the previous owner installed V Force 3 reeds and it sounds like its common for these to split or crack. I was also thinking I should check the flywheel for rust. I'm just not sure if either of these things would cause the symptoms I have. It would seem that the reeds or a rusty flywheel would make for a hard starting bad running sled. I was wondering if someone had a good suggestion before I check it out this weekend. Thanx.
 
The magic numbers they will stop revving at is 7900-8000rpm when you have a powervalve pulled thru the end. I would pull all 3 and check.

The reeds could also do that to some extent however usually they will make the sled run really rough down low(rich) and make it more difficult to start.

you can observe the flywheel with a flashlight between the recoil and the engine housing, look for flash red rust.
 
Okay thanx MrViper I'll check the flywheel first since that's the quickest and easiest. I cleaned my PV's this fall and adjusted them with the 2.5mm allan wrench method so I think they should be okay. If those check out then I'll move on to the reeds and see what they look like. I imagine its something simple. I'll let you know what I find. Thanx again for the advice. It makes it easier to have a plan of attack when trouble shooting.
 
Well I think I found out what's wrong with my Viper since I finally got a chance to work on it today. The first thing I checked was the stator since it was the easiest thing to check. It was quite rusty so I cleaned it up and put a light coat of WD 40 on it after. It seems to have better throttle response and on a stand it will rev up to 9000 RPM's now. We don't have hardly any snow, but there is enough to try it out in my field. Its fairly steep and the amount of distance I can hold it wide open is short. Its good off the line, but it kinda starts to fall off around 8000 RPM's. I don't know with an uphill pull that short if I'd be able to get much more than that, but the clutching seemed a little off. When my speed picked up it was almost like it was shifting up too fast. I thought this had stock clutching with the Bender Pipes that were on it. I've got it all stock now. So I took the clutches apart to see what I actually have for clutch components. They don't appear to be stock since they don't match the part #'s in the tech section. The rear helix had a # of CR11 and that was the only #'s I could see and it had a black spring. I didn't see any other colored marks on the spring. The primary has 8DN 00 weights and a black spring with maybe a white dot. I'm not sure since the white spot that was there wiped off with my finger. The engagement is around 3800 RPM. If my set up should be changed I was wondering what people thought of the 53/43 helix with the green spring and stock primary setup? Also where would you recommend getting these parts from? Thank you for any help.
 
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those clutch weights are from a 98 srx700, not what i would choose for a viper. Are you wanting to go back all stock or want it a little more peppy then stock? what kind of riding are you doing with it 90% of the time?
 
Wow they just bolted in SRX clutch parts, that would explain why it didn't work. It wasn't even that good with the pipes on it. Just about 100% of the time I'm trail riding and sometimes my wife rides two up with me to. I wouldn't mind getting a little more pep out of it as long as I have to change out some parts anyways. Oh I have another quick question. Should I worry about the inside of the flywheel since the outside was so rusty ? If you recommend pulling the flywheel I will need a puller correct. Thank you again for your time Mr Viper.
 
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So what would be a good setup for trail riding that's not too aggressive, but has more pep than stock. The HC setup sounds good, but I don't know if I have quite enough cash to cough up for that right now. Are my 8dn weights going to work at all with the right rivets or am I going to have to change them out ? Thanx again.
 
I see you were looking at the stock weights in the classiifeds, in my opinion those will work ALOT better then those 98 8dn-00 will, more peppy feeling,better backshifting for sure.
I would put the stock 8ek weights back in it, put 4.5 rivets in both holes, run the stock yellow/white/yellow primary spring, then add a multiangle helix like a 53/43, 50/44, 51/45 with a green dot sec spring at 70, this will wake it up a good amount and its cheap. Yes the h/c one is good but your right its also expensive.

(try to not go any lower then 43 finish angle on helix and no bigger then 53 on start angle, I listed a few differnt ones that work well)
 
Thank you very much for your reply Mr Viper. Clutching is one thing I've never played with so its nice to get some good advice to save time and money. That setup sounds just what I'm looking for, better than stock but not too aggressive either.
 
Well I got my clutch parts in yesterday. I got 8ek 00 weights and 4.5 rivets for both holes and a y w y primary spring. And I got a 53/43 helix and a green secondary spring at 70 twist. I really like how the clutching feels its nice and smooth for the tight trails around here. It will still only hit 8000 rpm though. I know I don't have a pull through and my PV's are cleaned and adjusted with the 2.5mm allan wreced method. I noticed when I got back that the previous owner tied the heated shield outlet into the PV test port. I didn't have my shield plugged in today so I'm not sure if this would this cause the PV's to not open? The sled runs great and it does almost seems like maybe the PV's aren't opening. This was something I thought looked out of place. I haven't had a chance to see if it would make any difference if I disconnected it or not. Just wondering if anyone thought I was onto something.
 
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1.)remove servo motor cover, start sled up, idle it down under 900rpm, does the servo acutate the valves?

2.)place sled up on a jackstand, start sled up with servo cover removed still, rev ther sleed up wide open a few blast, does the servo motor actuate the valves?
 
Okay I will try to check that out tomorrow night. I know when I adjusted the PV's I used a 12volt power source in the PV test port and the servo opened the PV's, but what you said makes sense since then the power source will be the machine and I'll know if its getting power. Should I leave the heated shield wire on the test port for the PV or does it matter ? Thank you again.
 
Well I tried what you suggested tonight and the PV's seem to be working fine. At 900 rpm they open up and when I hit WOT the PV's open again. Something weird though it'll hit 9000 rpm on the stand, but only around 8000 rpm when your riding it. It does pause a little around 8500 rpm then it goes right up to 9000 with the sled on a stand, it doesn't shoot right up to 9000 rpm. All of my electrics seem to work fine to. The hand warmers, thumb warmer, lights ect. and there's no warning lights either. The sled seems to roll easy down the trail, the track isn't to tight, and I have the chain finger tight and then 1/4 turn backed off. I really wonder if I have a cracked reed. There aren't too many things left that could cause it. Especially since the V-Force 3 are prone to cracking. And sometimes when I was out Sunday it was a little tough to start when it was hot. It would take 4 or 5 pulls sometimes even with the throttle cracked just a little. If it was a reed failing it would make a richer condition correct ? Thank you for helping me figure this out.
 
superfan75 said:
Well I tried what you suggested tonight and the PV's seem to be working fine. At 900 rpm they open up and when I hit WOT the PV's open again. Something weird though it'll hit 9000 rpm on the stand, but only around 8000 rpm when your riding it. It does pause a little around 8500 rpm then it goes right up to 9000 with the sled on a stand, it doesn't shoot right up to 9000 rpm. All of my electrics seem to work fine to. The hand warmers, thumb warmer, lights ect. and there's no warning lights either. The sled seems to roll easy down the trail, the track isn't to tight, and I have the chain finger tight and then 1/4 turn backed off. I really wonder if I have a cracked reed. There aren't too many things left that could cause it. Especially since the V-Force 3 are prone to cracking. And sometimes when I was out Sunday it was a little tough to start when it was hot. It would take 4 or 5 pulls sometimes even with the throttle cracked just a little. If it was a reed failing it would make a richer condition correct ? Thank you for helping me figure this out.
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u can't check the max rpm on a stand ..the clutch shift way to fast without load .....I think u should remove 1 gram from tip and try your sled again .....makre sure to wrap the helix at 70 ...yes it would run rich ...it wouldn't run properly at idle
 
well the only thing to do if everything else is good is to drill a small hole thru the tip rivet and ligthen them up some and grind a tad off the head of rivet, remove 1 grams from each tip rivet and you should pull the rpm then.

did you ever check:is it still stock gears?
 
I think its stock gears because I installed a reverse kit and it doesn't sound like there's much for gear selection. For drilling the rivets what size bit would you start with and do you drill through them ? I would probably need a scale to get them the same weight. Is it possible the servo isn't opening enough? Its opening maybe a quarter turn roughly, does that sound right ? It does stop at the same spot I marked with a marker when I adjusted them.
 
superfan75 said:
I think its stock gears because I installed a reverse kit and it doesn't sound like there's much for gear selection. For drilling the rivets what size bit would you start with and do you drill through them ? I would probably need a scale to get them the same weight. Is it possible the servo isn't opening enough? Its opening maybe a quarter turn roughly, does that sound right ? It does stop at the same spot I marked with a marker when I adjusted them.
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servo seem to work ok .....you definitely need a scale to do it ..u can grind the side of the rivets to remove some weight too...
 
The thing that I got to thinking about last night is weird is that when I got this sled it had triple pipes and it had this problem. Now I have stock exhaust and jetting and a different clutch setup and I still has this same issue. Something weird is going on in that it seems to run great until you pin it going down the trail and it'll only hit 8000rpm. With the back on a stand it'll 9000rpm without a load and the PV's are working. There's something going on that's is still there even with two completely different setups. This is a head scratcher.
 
take a black perm marker and make a line from the center of the front clutch to the top on the inside of sheaves where the belt rides. Do the same on the back clutch all the way from top to as far down as you can get it. I usually will open the rear clutch to get the line on the whole sheave.

take it out and run it wide open, shut it off, and take a picture of each clutch where it has worn off the marker on the sheaves.
 
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