MCX symptom on APEX Whats wrong?

[Boost It]

Installed two machines with mcx kit's.
They both have the same symptoms.
They run fine up to 7,000 rpm's, then they go into a stumble mode. (run rough)
What's Wrong?

 

[snowfix]

TORS?

 

[Srxspec]

cam timing?

 

[ripntear]

We had the same problem. I think they are becoming too rich under full throttle. That is when the extra injectors kickin. You should ask climbmaxs what he has done too his. He seems to have his dialed.

 

[Climbmax]

Any change in wiring?

Mine is dialed (haven't touched it since it went together......except an additional BOV B4 plenum) and I love it.

CM

 

[Turbo Tim]

I didn't think I was hitting the rev limiter when I first got mine put on , but I was. The engine will rev way faster than the tachometer can react. What do you have for clutching . I had to start out with a base (bare arms) weight of 65 grams. added 14 grams to each arm to finally get it off the rev limiter.

 

[obr]

had the same problem on mine, and, as TurboTim replied, it probably is the rev limiter.

Now, only problem I have, is that when I get to about 114 MPH (on the dream-meter) on the flats, I get a ratcheting noise... think it's because of the 7 tooth drivers with the low gearing and so much track to pull... enybody else experience this on their mountain?

 

[slymax]

Any codes coming up on the dash? The only time mine pops is under rapid acceleration (full throttle) on the trail. It works fine the rest of the time. The thing revs so fast it can be deceiving, sounds like rev limiter or TORS, if it's TORS you may have a code displayed.

 

[Big-zig]

Check cam timing. I bet you are off one cog...

 

[sledheadgeorge]

Check cam timing. I bet you are off one cog...

I agree

 

[slymax]

For sure, that would do it and you wouldn't be the first. The cam timing can be a little tricky if you are unfamiliar with twin overhead cams. I have worked on lots of twin overhead cams over the years always double check. After you get it all back together it is important to rotate the engine 2 full turns by hand and recheck the marks.

 

[Boost It]

Thanks for all your suggestions.
1. TORS is bypassed.
2. TPS checks out.
3. Rechecked cam timing . (appears to be fine)
4. installed extra BOV in charge tube hose.
5. recheck wire hook up
6. No codes appear on the dash.
7. blowing out valve cover gasket.
8. running 8BU00 with two 4.5 gram rivits.

9. These are the early build kits. we think it's the efi boxes ( it sounds lean from 7000 to 9500 rpms) check mcx injertors for flow, check OK.

10. still trouble shooting. (hours and hours..... of hours into this.)

THANKS TO ALL ! I'll Keep you posted.

 

[rxrider]

Boost It - You run 8BU00, they are like 48.7 grams with little tip weight and you have added 9 grams to total at 57.7 grams each. IMO you run too little weigth and are hitting the rev limiter big time. What primary spring do you have in. I have a Blue-Silver-Blue 35/101 HHs at 66.5 grams, I hit the rev limiter in no time. I need more weight. I think you have to add more weight up front.

 

[snowy1]

the 8bu-00,s are alot more aggressive which means you can run less wieght in them, depends on what boost he is running, I am running 18lbs with them welded up to 61 grams at 10,000-10,200 rpm at 10,000 ft.

 

[givemeaboost]

I'd do a compression check before you go any further. If you're blowing out the valve cover gasket you might have more serious problem like too much blowby . Did you use race gas to run that 14# and what elevation were you at, North Dakota isn't very high in elevation , Ken.