Nytro MCX issues...small but a PITA

[Thistledoo]

OK I got a couple things I need to get sorted out

First thing....everytime I trench her down with the A$$ end low I let it idle and cool down....shut it off....dig it out and when i fire it up it throws some oil out the exhaust side...like enough you can see it on the snow. Anybody seen the seal in this turbo?? I understand its like a piston ring....cant really go bad. Maybe my return pump is bad at idle and cant suck the oil back?? Any sugestions??

Second thing. I have the standard 8BU's weighted up with the violet EPI spring 47deg helix.. and I have roasted 2 belts in the last 4 rides....like strings stickin out. The last few rides its been crazy deep and I have been breaking trail everywhere....but still my clutches are smokin hot....has anyone geared down?? Still at 20/40....does yammie make a 42 to go with the reverse?? Maybe 19/42 would help. Maybe I need some more venting or diff clutching?? Help!! Any ideas??


Thanks guys...fire away....I need some ideas to get this stuff sorted out.
Today was one of those days I'd been better off stayin on the couch!!

 

[M5-]

Don't know if the gears themselves are the same or not but I run 19/40 on my TRX and I've never blown a belt (touch wood). MPI made a 42 tooth for the Rx chaincase. Knowing Yami the gears are likely the same. The problem with the 42 is you have to machine the idler gear down a bit in order for it to clear the big bottom gear but 20 42 would be easy on the chain and give a good ratio. My buddy ran 21 39 reverse from a flatl land sled and burned a belt in 1 day, now he's got 19 39 so far so good. I haven't run Yami weights in years too much of a PITA to get right IMO.

M5

 

[DARKO]

Oil from the turbo is a strange one, 2 ways that can happen (other than a seal which i highly doubt it would be) --- Return Vent line plugged, or oil return pump off the crank snaped the sheer pin. Pull off the vent line and blow thru it, if thats clear take off the housing cover for the oil return pump, if you can free wheel it the sheer pin has broken.

 

[PwdrNut]

As far as gearing goes:
You can get an 18 top from Yamaha and it will be close to the 19/42 gearing.

 

[snowy1]

On the oil I don,t no other than what Darko said, gearirng shoud be ok, lower would not hurt I may try it myself. but the 8bu,s work great on mine with stock gearing, I know there,s been alot of guy,s say to us the cat secondary springs or epi and not yamaha. I have been running the yamaha secondary springs with a 47 helix for 4 years on my TRX and know on my nytro wound to 100 degrees works fine. no belt problems ever. I assume you have the 14.5 rollers in the primary.

 

[Thistledoo]

Yup small rollers. Wonder if I put a 19 top in there if that would help much?? Should fit with the stock chain right? 18 would be pushin it IMO...anybody doing it with boost? I will check the pump drive and vent lines....something is definatley up. Is there anyway that the pump can get starved of oil and maybe got scored up abit?? Like it seems to run fine when its wicked up....but when idleing with its tail down maybe it doesnt have enough suction to pull the oil back?? I will take it apart tonight after its unthawed.

 

[Stlhead]

If you go to the 19t top you should change to the 68 link chain. I did this on my NA Nytro and found it helps a great deal with low speed maneuvering as well as starts. Should work the same for a turbo before the boost comes on.

 

[Thistledoo]

Well I pulled the return pump apart and its shot...pretty gawled up on the end plate so it wasnt suckin when idleing....I'm sure at higher revs it was pumping ok. Kinda what i thought. At Install I completley filled the oil lines with a syring....and it ran fine for 3 or so days. Wonder how I damaged it?? I'm runnin yamalube 0-30 semi synthetic?? Anybody seen a pump go south before?? Hope someone has one in stock

 

[0007]

Check and see how snug the pump parts fit together, if there is a lot of tolerance it might have weak suction at low RPM

As for belts, did they blow at high speed or low?, hi speed usually means secondary slippage and low speed usually means primary slippage

 

[Thistledoo]

Jeff the pump is scored pretty bad....like finger nail deep on the end palte....makes perfect sense....thats why it wouldnt suck when the A$$ end was low...but when reved up it still created suction. So is it my fault and what did I do wrong?? Dont want it to happen again. Wonder if MC will look after it

 

[Thistledoo]

Update Update

Well I finally found some time to tear into my sled for this years changes and updates...heres what I found after 20 good ride days....

First as below I had some issues with the oil return pump...the replacement looks good with very minimal scoring....the original was warrantied because it was built wrong with too much end load on the rotor.

Second....pulled the header off expecting to find all is good....wrong!!
right where the factory welds the 3 into one...pu$$y little 1/8 wide welds are all starting to crack....my weld where we welded the turbo flange on is perfect...new header time....anyone else seen this??

Third...last few ride I noticed a small leak up above the primary clutch...like oil...looked it over but couldnt see anything.....thought maybe it was from laying it over ect. Well tonight I pulled the charge tube and guess what I saw...the 1/2 circle rubber plug thats built into the valve cover gasket was pushed in from the charge tube rubbing against it...the tube is a very tight fit and now I found the leak....just a heads up to check. I think a small gaurd will have to be fabbed up to protect it or something.

Fourth...chaincase bolt after I replaced it with a 10.9 metric was broke again a couple threads into the drive axle....not sure what the fix is here...I d say it had maybe 6 or 7 hund klicks on it and its been broke for a while...anyone got a fix?

Fifth....rear timbersled cross shaft was bent 1/8 inch...not much but just enough so you cant get the cross shaft out....Sent it to Allen and Budd a month ago and they are looking after it

Sixth....my avid drivers look flawless....my yammie sliders are done...no biggy a season is fine wear I think.

If anyone else has some things to add feel free...I'll post some pics when shes going back together.....

 

[SNOW JW]

How many miles do you have on the gal???

Also the AC green snowpro spring works good as well.

 

[modsledr]

A/C Green spring/Shockwave...19/42...also bent top shaft on my Mt Tamer, Alan replaced w/updated rear arm. Hyperfaxes look great after 10 spring rides.

 

[dexter]

I discovered my header months ago when installing cr tunnel, mine tore through on the brace weld also. I will have to check my charge tube, hopefully its fine.

 

[Thistledoo]

I forgot to say I did install the green AC spring and it works great....good thing to have a spare in the toolbox too.

THe rubber charge tube is fine on mine....but it pushed in the rubber plug causing a oil leak....cant believe more oil wasnt coming outta there.

 

[Turbo Tim]

Oil from the turbo is a strange one, 2 ways that can happen (other than a seal which i highly doubt it would be) --- Return Vent line plugged, or oil return pump off the crank snaped the sheer pin. Pull off the vent line and blow thru it, if thats clear take off the housing cover for the oil return pump, if you can free wheel it the sheer pin has broken.

When you're trenched down with the back way down , all the oil from the return lines drains back into the turbo , the turbo isn't spinning so the seal isn't working . I thought mine was gonna catch fire here .

 

[M5-]

Now that's a trench!!!!

M5

 

[Thistledoo]

I know what you mean about on fire....kinda sucks when she pushes out the smoke....takes awhile to burn it all out too

[/IMG]

 

[up-high]

Now that's a trench!!!!

M5

From the size of that hole, it looks like you should have struck oil!

 

[SNOW JW]

Holy cow I feel sorry for the poor sucker that comes along and goes nose first into one of those trenches.