MCX 240 Clutching/Performance??

[Brutis20]

Another new guy to the Tnytro. 08 Nytro w/ 240 MCX kit, 162, Shock Wave, on premuim, believe stock gearing 20-40.

Had it out for the first time in the hills yesterday, it pulled great down low at 2600 ft running ~ 8900 RPM when opened up and ~ 13-14 psi boost 9not sure of track speed, never thought to look, plus it was a blur!

Once we got up a bit to 4500 ft, noticed the sled didn't run as crisp, not really bad but just noticable. Would pull 14 psi but only would get 8300 RPM out of it (still hauls!) but not as "clean" feeling (suspect icing on this). Seemed like it had to work a bit harder to get up and going.

My question is if its normal to only go 2000 ft and see this type of change, I would assume not. I did have my air filter icing up a bit, would clean in and it would run cleaner, but still could't pull RPM's like below. Once we got back down it ran great again. just seems funny with only 2000 ft elev difference.

I know I need to find out clutching more detailed, and will do that tonight hopefully, if it is this? Only other thing I was thinking would a small leak in the exhaust pipe or boost pipe do this even though I was still pulling boost - seen this happen on an APEX but it was more noticable.

From what I know so far is: primary has a Back/Purple mark Spring?? 14.5mm rollers, not sure what weights. Secondary has the Shock wave and looks turned in quite a way - would guess 1 or 2 out (will check), and Black with a white mark spring.

If its clutching, I can work on this, just wondering what direction of trouble shooting I should head.

Thanks

 

[summitboy]

I'm no expert on the Nytro but I believe most run the following:

Blue white blue prime spring
Arctic Cat Green p/n 0748 025 sec spring
14.5 rollers
Shockwave set between 47 and 50ish (wound at either 10deg or 30deg, can't quite remember )
Yamaha 8BU fully loaded weights

That should be close. Some might chime in and tweak it a hit for the 240 kit. Sounds like you have stock in there. That's your first problem.

 

[Tarzannr1]

Another new guy to the Tnytro. 08 Nytro w/ 240 MCX kit, 162, Shock Wave, on premuim, believe stock gearing 20-40.

Had it out for the first time in the hills yesterday, it pulled great down low at 2600 ft running ~ 8900 RPM when opened up and ~ 13-14 psi boost 9not sure of track speed, never thought to look, plus it was a blur!

Once we got up a bit to 4500 ft, noticed the sled didn't run as crisp, not really bad but just noticable. Would pull 14 psi but only would get 8300 RPM out of it (still hauls!) but not as "clean" feeling (suspect icing on this). Seemed like it had to work a bit harder to get up and going.

My question is if its normal to only go 2000 ft and see this type of change, I would assume not. I did have my air filter icing up a bit, would clean in and it would run cleaner, but still could't pull RPM's like below. Once we got back down it ran great again. just seems funny with only 2000 ft elev difference.

I know I need to find out clutching more detailed, and will do that tonight hopefully, if it is this? Only other thing I was thinking would a small leak in the exhaust pipe or boost pipe do this even though I was still pulling boost - seen this happen on an APEX but it was more noticable.

From what I know so far is: primary has a Back/Purple mark Spring?? 14.5mm rollers, not sure what weights. Secondary has the Shock wave and looks turned in quite a way - would guess 1 or 2 out (will check), and Black with a white mark spring.

If its clutching, I can work on this, just wondering what direction of trouble shooting I should head.

Thanks

Hi
If you have a small leak in the exhaust pipe you HAVE TO GET IT FIX if not you will get bigger boost problem in a while.
If the sled doesnt stops when you close the exaustheader with your hand then you have a leak. If the sled stops right away then you probably are fine.
I had a leak in the exaust here
.

.
.
And had also leak here on the exhaust donuts
.

.
.
.
Got some new copper donuts from zipperno here at snowest send a PM to him if you want some.
.
Precision turned copper.
Specifically designed to withstand heat and exhaust pressure for mid / rear mounted turbo.
Fine solution for those who are tired of changing these mid-season.
can of course be used on standard engine also.

would have been much cheaper to made those out of brass,
but then you lose the ability to remain soft under heavy heat/presure
.
Use copper to get the best possible sealing under heat pressure and have the best possible life.
Copper is soft when it gets hot and will close better than brass or aluminum.
the problem with the stock
gaskets that are leaking very fast once you get a leak, and they're even worse with the turbo.

Zipperno here at Snowest forum is the man to PM.

100 USD quantity of 3 that is cheap very good price remember this is good copper! Run and buy from Zipperno i am shure you will have it in no time from him since him is handeling export out from Norway and i am shure of if you buy 50 ore 100 of those you can sell it for more than 100 , those donuts works!
.

.

 

[Brutis20]

So I went over the exhaust sytem and couldn't find any obvious leaks, put my handle over the tail pipe and takes probably 5 seconds to kill the engine, can't hear anything leaking.

Checked out the clutching and the Primary has a Blue/Brown/Blue primary spring (brown looks more red but only could find the BL/BR/BL in the book). The rollers are 14.5 mm. As far as the weights they look nothing like anything in the manual, have 2 holes close to the base but are empty. I weighed one and it was 89g also looks very flat! This could be part of my problem. i will try and get a picture up.

Secondary has shock wave. It was 0.5 turns out. Have a black primary spring with just 1 white mark on it. Anyone know anything about this?

From what I have been reading this is way out, so i will probably switch to the recommendations.

I am thinking it is the clutching.

Just wanted to clarify the elevation issue, what would be a normal range that would actually effect clutching on a Tnytro like this? I am thinking it would need to be over a 5000 ft difference to move rpms by a couple hundred rpm? Whats you guys experience?

 

[Tarzannr1]

When i was driving mcx 240 ,i gear it down one tooth on my xtx and i went for a black heelclicker spring in primær clutch and stock spring in secunder clutch
And stock helix went for Heavy Hitters weight
Base weight 67,6 gr
3,3 gr inn pinn
bolt 5,8 gr with 1,4gr washer
and on the tip bolt 4,2 gr with 1,4 gr washer on

Totaly weight 83,7 gr with stock helix 43

and that was a superb setup for xtx with mcx 240 ,With this setup, most of them who had Nytro 270 kits did not stand a chance against my 240

Think you have to look at your shockwawe what angle that is on .And if you dont wanna try my setup here is what Ulmer says for mvx240,
Set shockwawe for 42 angle and go for supertip weights base 60gr and load it up to 76gr
and go for a green sorry to say Articat spring

Good luck

 

[evil1]

gonna try my 240 kit the next couple days,,will let ya know how it feels,,I was definetly feeling the same rpm's--low track speed as i got up in altitude last year with the 180 kit,,I'm thinking if i exsperience the same i'm going for the top 19tooth

 

[Brutis20]

Here are some pics of the weights. Anyone know what kind these are? Also the Primary spring and the secondary. Are these yamaha? I would guess so from the book. What is that Arctic Cat Secondary part number that is working? Anyway let me know what you think.

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[canucklehead]

It's the arctic cat green spring... 0748-025.

You got some custom weights there for sure, looks like somebody was even modifying them. If you go with the 8BU's like most guys do make sure you get the 8BU-00 and not 8BU-10.

You could try the secondary for starters but that's a lot of weight to be swinging. You could lighten them up but do it on the underneath side and take most of the weight off of the tip section.

 

[Wheel House Motorsports]

those weights you got are a pretty flat curve, so once you start really loading hte motor up with bigger hills, less air etc, its gonna make the lag worse as the weights are not letting the motor rev up right.

and you shouldnt be loosing that kind rpm.. a little, but nothing like that.

also, the cat secondary spring is like $25.. another easy thing to do and you know your heading the right way then.

 

[TBird]

The weights are MCX turbo weights, look's a little modded, somebody tried rise engagement?

 

[TBird]

This pic is from a couple of years back, some of my weights lined up.

 

[Brutis20]

Cat green spring - Twist Rate?

Ok, thanks guys this is some great info, I did have the MCX weights, this site is #1! I have been combing the clutching sections. I have switched to the BWB primary, fully loaded 8BU's, and went to a Cat Green secondary.

My question is what are you guys running for twist rate? I set it at 110 deg (#2 on plate and #9 on Spring - shockwave side). shockwave set at 1.5 turns out.

Is this too much twist on this, I seen some guys running 0-1 which would equal 10 deg? Doesn't make sense?

Let me know what has been proven.

Thanks

 

[Summitseeker]

I had the same MCX weights in and was blowing a belt every few hundred KM. It switched last season to the same setup that Summitboy suggested and the problem went away. You could still have a boost leak though....I would check the donuts as Tarzannr1 suggested. I checked my donuts before the start of the season and two out of the three were toast and the other was worn badly.

 

[Brutis20]

I am going to check the exhaust again since I want to check my plugs anyway it will be easier this way.
summit seeker:
Was it obvious that the donuts were gone, or how did you check these? I didn't notice anything when I checked before, when I put mu hand over the end pipe it took about 4 seconds to die, not sure whats normal.

You remember what you set your spring at (deg) for notches in your secondary and plate with that cat spring?

Again I really do appreciate all the great help.

 

[Wheel House Motorsports]

I know on mine I wound my cat green spring to 10*... the lowest setting and it was a PAIN to even get it in place.. not sure if you will have much luck trying to get it wound farther.

 

[Summitseeker]

summit seeker:
Was it obvious that the donuts were gone, or how did you check these?

When I opened mine there were only some wires and a bit of material left on two of the three donuts. I had new ones already purchased so it was clear they were toast. I am sure these gaskets would last much longer on a non-boosted sled.

 

[Brutis20]

Oh, it was a chore to get it to 110 deg. Like I said this is with it set in #9 on spring cap and #2 on the Spring Sheave. From the yamaha book it would be (9+2)x10= 110º. Correct me if Iam wrong or if this will be wound too tight and not back shift properly?

 

[TApeX_07]

Brutis- Im surprised you were able to get it there! I dont think itll upshift very well and if it does, its gona backshift HARD!

 

[Brutis20]

So the 0-1 @ 10* is the general consesus to run this at? Just want to make sure before I pull it apart again. For what it took to get it set here I am also thinking the same thing. Just want to know what has been proven.

thanks

 

[mitty26]

i got my green spring at 0-1 as well.