Loosing RPM during climb

[loudelectronics]

Not sure if I am getting clutch bind in the secondary or something else is going on.

Sometimes when I climb I lose RPM. It is clutched for 8700-8800 but the odd time when in WOT on a climb the rpm will not get above 7600 and gradually drops to 6500 by top of climb. Periodically during mid climb the rpm will jump from 7000 to 8800 and it pulls like a raped ape under full boost. So not sure if it is boost related or clutch related.

8BU weights, green spring, 39* helix and white spring. MCX 190.

Not sure what the boost is under the load cause my boost guage at elevation is all over the place. Vaccum goes to -14 and boost sits around 0-4 psi at 10,000 feet. At home 2000' l i see 5-6 lbs.

 

[moto5151]

I would say clutching for sure. Ramps, or spring broken somewhere. Pull it all apart....

 

[174mcx]

I don't have much experience with a mcx 190 kit but I would look at an exhaust leak, If theres a leak it will not pull hard when the going is tough but when the load decreases (say coming over a convex) it will spool up again and seem better. I had a apex with a mcx and it would do this.

 

[climbmax]

And you have a nice cold Air supply right?

 

[loudelectronics]

I have a cold air intake/snorkel. That made a huge improvement right there.

The clutching is all new components so should not have anything broken. I just recently had it apart as well to verify.

I will take a look for an exhaust leak as it does as you say 174mcx. This is just under severe load. I am wondering if I have a leak on the connection from the header to the turbo as there was only 3 bolts originally and I had to add another as the flange appeared to be bending.

 

[bigfish]

I have a cold air intake/snorkel. That made a huge improvement right there.

The clutching is all new components so should not have anything broken. I just recently had it apart as well to verify.

I will take a look for an exhaust leak as it does as you say 174mcx. This is just under severe load. I am wondering if I have a leak on the connection from the header to the turbo as there was only 3 bolts originally and I had to add another as the flange appeared to be bending.

you ever replace your exaust donuts.

 

[174mcx]

It could be the pipe to turbo connection, like I said I don't have experience with that kit or a nytro really. If it was a Apex it would be a exhaust donut, bellows or Y-pipe, these where the the only parts that where still yamaha parts and not designed to hold the back pressure created by a turbo and would cause problems. The pipe that attached to the turbo on a apex was made by MCX and built out of Stainless and built well for the application. If its a exhaust donut you can get copper ones that last alot longer than stock

 

[loudelectronics]

I should mention that this is a viper.


I made some modifications that Climbax told me and made a big difference this year. Just this one has popped up now since I could actually use it now.

The header is known to leak at the turbo connection so it could be the case.

Otherwise it is clutching I am thinking.

 

[climbmax]

I can't imagine running that helix. Gotta get those 4 strokes upshifting to build speed.
190 kit should read something like this
8BU-00 with maybe some small rivet in the heel
14.5 rollers
Blue/white/Blue primary
47 degree OEM secondary
White secondary spring @ 6-1 or 70 degrees

Should pull like an animal. And hold RPM on the hill

Cheers

 

[174mcx]

I don't have the experience Randy does but a shallow helix should promote a back shift I think...

 

[bigfish]

yes have never seen anybody run that shallow a helix on the 1049cc always 45-47 degree.

 

[loudelectronics]

I am pretty sure it is a 39* helix. It is out of a nytro mtx. I thought the viper mtx ran a 37* helix with pink spring? I believe my machine came with a 47* helix as an xtx but not sure what it was. I could try it if it were the case.

The sled has torque for sure. Climbs like a mountain goat and keeps pulling even under the low rpm. I just know when it does decide to shift up into the 8800 it really rips with tons of track speed. That is where I want to get too.

 

[lightening1000]

I run the 37 helix with a black dalton spring and like it much better than the 47degree with purple epi.. Little more zingy with 37, not so lazy as the 47 is..it pulls good track speed and has awesome backshift. Just have to load the primary a bit more for the helix.