Quick Question for anyone that has solved WOT rpm issues with the TPS adjustment

[Perk]

Thanks in advance for your help. I have had top end rpm issues once before. After about 600 miles. I read a lot of posts on here and decided to just haul it down to Carls and have them throw an SLP pipe on it and check everything. I was hoping that would give me some margin. I say margin because it seemed like my sled was always on the edge of pulling rpm on the top end. When everything was new, there were no issues. Dropped it off at Carls, had them pipe it and clutch it to their specs. They ended up adding an SLP torque arm (my request), threw on the SLP pipe, added their clutching and replaced the motor mounts, went through primary and balanced it. Got it back and it would only pull 7900, but with the pipe, you are running heavier weights and a different helix angle (Carl's setup). So I switched the helix back to the other angle they offer, which I am pretty sure is the stock angle. Sled pulled 8100-8200 so I was happy. I rode about 400 miles this year. 2 trips ago, I was climbing at pretty high elevation (9200 ft) and I looked down at the tach and it was pulling 7600 -7800. Not a good feeling for the climb I was pulling. Next trip, easy ride but I made a few pulls and ran a few drag races and I was only pulling 7700-7800 and elevation was only 7k.

So I decided to check the tps. Because this sled can run, but it seem like everything has to be perfect (likely in the clutching). I checked my tps today and the pre-adjustment results were Base = 0.737, Idle = 0.931, and WOT = 4.28. At these settings, I have never had any issues starting or going into reverse. So I am not concerned with that, but am curious if my voltage at WOT could be the issue. I restet it up to Base = 0.701, Idle = .940 and WOT ended up at 4.25. So could 0.03v at WOT really be causing my rpm issues? Or is it more likely that I am just that sensitive to belt wear? Belt deflection is always adjusted and I have about 500 miles on the gates CF belt. Pulled my power valves while I was working on the TPS, seemed pretty clean - cable travel was in spec. there was some residue on the back of the top blade that may have kept it from opening all the way (on the outer sides at the back of the valve) but could not tell, I would expect a code for valve position not reached if that were the issue. Ok, think I have spilled all that I know. Main question for you is "could going from 4.28v WOT to 4.25v WOT actually be the issue - does not seem likely to me that .03v would make any difference. Need to figure this out because if this isn't the issue, I am snow checking an 850.

Cheers,
Chris

 

[Sheetmetalfab]

Thanks in advance for your help. I have had top end rpm issues once before. After about 600 miles. I read a lot of posts on here and decided to just haul it down to Carls and have them throw an SLP pipe on it and check everything. I was hoping that would give me some margin. I say margin because it seemed like my sled was always on the edge of pulling rpm on the top end. When everything was new, there were no issues. Dropped it off at Carls, had them pipe it and clutch it to their specs. They ended up adding an SLP torque arm (my request), threw on the SLP pipe, added their clutching and replaced the motor mounts, went through primary and balanced it. Got it back and it would only pull 7900, but with the pipe, you are running heavier weights and a different helix angle (Carl's setup). So I switched the helix back to the other angle they offer, which I am pretty sure is the stock angle. Sled pulled 8100-8200 so I was happy. I rode about 400 miles this year. 2 trips ago, I was climbing at pretty high elevation (9200 ft) and I looked down at the tach and it was pulling 7600 -7800. Not a good feeling for the climb I was pulling. Next trip, easy ride but I made a few pulls and ran a few drag races and I was only pulling 7700-7800 and elevation was only 7k.

So I decided to check the tps. Because this sled can run, but it seem like everything has to be perfect (likely in the clutching). I checked my tps today and the pre-adjustment results were Base = 0.737, Idle = 0.931, and WOT = 4.28. At these settings, I have never had any issues starting or going into reverse. So I am not concerned with that, but am curious if my voltage at WOT could be the issue. I rest it up to Base = 0.701, Idle = .940 and WOT ended up at 4.25. So could 0.03v at WOT really be causing my rpm issues? Or is it more likely that I am just that sensitive to belt wear? Belt deflection is always adjusted and I have about 500 miles on the gates CF belt. Pulled my power valves while I was working on the TPS, seemed pretty clean - cable travel was in spec. there was some residue on the back of the top blade that may have kept it from opening all the way (on the outer sides at the back of the valve) but could not tell, I would expect a code for valve position not reached if that were the issue. Ok, think I have spilled all that I know. Main question for you is "could going from 4.28v WOT to 4.25v WOT actually be the issue - does not seem likely to me that .03v would make any difference. Need to figure this out because if this isn't the issue, I am snow checking an 850.

Cheers,
Chris

to check/ fix in order of probability/ importance.

worn motor mounts.

stretched EV cable ($40 easy swap)

worn out primary clutch (new take off clutch is easiest)

Carl’s clutching can’t come close to Indy specialty or TRS’s setup. (Pitch it and replace)

 

[Perk]

Thanks Fab - motor mounts have about 400 miles on them since replaced (maybe they are due again), I checked the EV actuator cable travel and it was dead on spec. Primary was also rebuilt 400 miles ago (and balanced). As for Carl's clutching, maybe I need to try another combo but I ride with another guy that has my exact same setup (except he just switched to lower gearing) and he has been pulling rpm fine (both before and after the gearing change).

Still hoping someone can answer if my baseline adjustment might have helped here before I change anything else. We have a lot of guys on here that chased rpm issues and many of them tried the TPS adjustment to see if it would resolve the issue. Hoping someone can comment on weather or not they saw an improvement in holding rpm especially if their baseline (pre) was similiar to mine.

Thanks for your input.

 

[AdrenalineAddict]

An experiment you may want to try is take a look at your secondary with the Carls Helix and make sure you are running the black/purple, then drop your primary weights a couple grams even if your buddy's sled can run more weight, might still run side by side. Deglaze your primary faces with a scotchbrite pad and also deglaze your belt with a scotchbrite pad, this helps a lot with backshift (more grab will make your secondary feel more resistance and will improve backshift). I've found deglazing will give me 200 R's time and time again. These 800's are very finicky machines to get running perfect, been fighting them for years. Your TPS voltages are exactly what my good running Axys reads, just checked the other day. I don't own an 850 but I have heard through the rumormill they are much less finicky to set up and tune.

 

[Murph]

If I read your post right, your primary has 1000 miles on it-- 600 miles before rebuild, 400 since rebuild, correct? Axys 800 motors eat clutches. Was the moveable sheave bushing replaced? cover bushing replaced? weight bushings replaced? If any of those allow the clutch to get c0cked it can prevent full rpm.

400 miles on belt? Test with a new belt to see if rpm is any better.
How old is the primary spring? Another cheap test.
Does it run any better/ different in Eth/ Non-Eth mode?
Have you tried swapping EGT sensors with someone whose sled is pulling good rpm?

Lots of little things will take 3-400 rpm away. The difference in feel between 7800 and 8200 rpm is HUGE.

Is the rpm with a hot/ heat soaked pipe? The pipe needs to be hot to pull full rpm. The aftermarket pipes don't have the clamshell and they really need to have the heat in them to pull rpm.

 

[A@ron]

murph have you had any good results with the stock pipe wrapped with header wrap?

 

[Murph]

murph have you had any good results with the stock pipe wrapped with header wrap?

header wrap instead of the clamshell?— tried it back in 2011.
Pain to wrap
Pain to keep it tight.
It still shed fiberglass hairs.
Seemed to trap more moisture then clamshell.

stock clamshell makes a mess when the insulation vibrates out, but it does hold the heat in pretty well.

aftermarket single pipes work good on the 800– when you allow them to warm up. They are pretty doggy after a longer delay— until they heat back up again.

 

[Perk]

Thanks Murph, I think you and I are on the same page (belt/clutching). That is why I posted the question about my TPS adjustment. I don't think it was the issue, but if someone had seen a big difference in pulling rpm after the TPS adjustment (especially if their pre-base was similiar to mine) I would hold off on diving into the clutching again. I don't remember what all was replaced when they re-built my primary. I will call them and go over it. But clutching is next on my list.

Pipe had to be hot last time I tested. I made ~10 400 yard pulls back to back - no difference. I'll go after the belt next if RPM's aren't back. I deglazed my clutch faces and gave my belt a good scrub before I put it back together. Belt looked fine, but I did not take any measurements on it.

I have seen a few posts here recommending using the new 850 belt. One guy said it was good for 200 rpm. Anyone else have experience running the 850 belt on the 800 Axys?

 

[Murph]

I have seen a few posts here recommending using the new 850 belt. One guy said it was good for 200 rpm. Anyone else have experience running the 850 belt on the 800 Axys?

Don't forget swapping in a new primary spring...

The 1216 (850)belt. On my 850, it does gain 200-300 rpm over the Gates in back to back comparisons--- but for the wrong reasons. The 1216 is slipping in the primary allowing the extra rpm 300rpm/ 60 seconds= 5 revolutions per second. The 1216 is a tough belt, it will take the heat buildup of that slipping but I prefer the Gates. The Gates has a lot better grab out of the hole. BUT, the Gates is not as resistant as the 1216 to clutch misalignments.

 

[Perk]

Thanks Murph - Started this year with a new belt, primary and secondary spring and I adjusted the TPS late last spring (no chance to test after the TPS adjustment) RPM issues are gone. Going forward, I will start with the springs and the belt.