M7 Won't run RPM's

[drovdal@srt.com]

I bought my first M7, a 2005 about 8 years ago, another a couple years later, and just picked up another 05 (I have a couple of Pro's too). I have 2 teenage boys and the M7's perform great and take the beating that they dish out, lots of miles on the first 2.

The one I just bought won't run over 7400 rpm's. The previous owner disclosed that it wouldn't run absolute top end. I thought I would just start switching parts and figure it out. I swapped secondaries, the one I put in it had a new spring, went to factory exhaust instead of a can, and put a new primary spring in. It still won't go much over 7200.

It seems like it gets to where the power valves need to open and they flutter. after switching the clutching and exhaust with no change I decided to take it outside with no belt on, warm it up and rev it. It would jump up to about 7500, and then back down and not go past 7100. I'm at a loss, I have fixed rev issues on my other M7's by things as simple as changing the belt, going back to factory exhaust from a can, putting new springs in, cleaning the power valves, etc. but I am wondering if anyone has any ideas to try.

The new M7 has 1700 miles and the previous owner put a new top end in, new stator, and new ECU. Is there a rev limiter that could be bad? Servo motor on the power valves?

Thanks for any ideas.

 

[Bradley T]

I have had several M sleds and they real power comes when the power valves open. I would do a couple of things: Check to insure the power valve cables are not bad (disconnect them from the servo motor and pull on them. If you can pull and release them and hear them click, you are good). Second, make sure the power valve cables are adjusted correctly. You can search another forum and see the measurements. Also, if you move your servo motor, make sure it rotates back to the original position when you first start the sled.

To me, it sounds like a power valve issue. When you start it and jack up the back end, can you hear the power valves open when you hit 6,500 RPM? The sled has a totally different sound when it hits the power band.

Good luck.

 

[drovdal@srt.com]

M7 Won't hit top RPM's

Thanks for the tips on the power valves. I took them out and cleaned them up, they seem to move pretty free, no issues with the cables moving. I took the cover off the servo motor and moved the PV's manually, seemed to be in sync as well. Ran the sled with no belt and watched the servomotor open them up, as it went up the servomotor would fully pull them open, and then when it got to about 7500 rpm's they would start to alternate to closed and then open again.

The sled has aftermarket reeds in it, I may try to put a set of stock reeds in it and see if that does the trick. I have put new fuel in it and tried swapping ECU's with my other M7 that is running great, no change when I did that.

 

[boondocker97]

I'd swap servo motors between the two sleds next. Seems that one has an issue staying open. Maybe getting weak?

 

[Bradley T]

I agree. Try changing servo motors BEFORE you change the reeds. Changing the reeds on the M sleds isn’t easy. The reeds shouldn’t effect the servo motor opening and closing.... just a thought.