As the title suggests my 21 won't rev past 7k. It idles fine, pulls fine up to 7k and then won't go any higher. The bike has 15k on the odometer, appears to be all stock sans a set of Tyga canisters.

Any help will greatly appreciated!

Thanks-

Doug
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dd

www.raresportbikesforsale.com

At a guess, that's just after when the powervalves open up. Have you checked them to see if they are operating normally?

Do your basic checks like check your air filter, your carbs aren't blocked, float heights are correct and you can get teh throttle to turn the full way.

Check your PGM to see if it has suffered any damage, and like Middo said, check to see if your RC valves move freely.

The valves are cycling when the key is turned on and between 2-3k as for opening up at 7k... well, it stalls to just before it.

I'm going to start with the easy stuff like air filter, plugs, and carbs.. I'm going to search the site now for the various plug types.. I know they are 8' and 9's, but not sure which ones should be used.

Forgot to add....

I looked at the PGM today and it doesn't appear to be damaged, but I wouldn't know what to look for either...LOL! I'm a life long 4 stroke guy who has been recently converted ;o)

Has the plastic case been damaged or look likes it has been pried off before? When you smell the thing, does it smell like burnt electronics?

I'll get my sniffer out tomorrow...

Does the exhaust smoke smell strongly of petrol? Any black gloop from the exhausts?
Has it been stood for any length of time?
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it wouldn't be fun if it was easy!

dunkenb wrote:Does the exhaust smoke smell strongly of petrol? Any black gloop from the exhausts?
Has it been stood for any length of time?

Not really, it smells like cotton candy to me, but seriously, it doesn't smell like raw unspent fuel. As for the exhausts, I did a pretty good inspection of the cases last night looking at the RC valve function and there wasn't any goo present. I can't speak for how long it's been sitting, but I plan to tear into it tonight and look at the carbs, reeds, and piston skirts.

after a detailed inspection I found the lower cylinder was scared pretty badly so I sent them to be tidied up. I figured this was the problem with the revving issue that I discribed previously. While I had it apart I checked the reeds and all were good. I cleaned the carbs and checked the air filter. I ordered a new top end kit from Tyga and have since put it all back together.

I heat cycled it 5 times using 30:1 premix with Motul 710 and avgas. After much anticipation I took it for a spin tonight and was going to take it up to 8,000 rpm's continuing with the break in.

As it appears I am now back to square one because it still won't rev past 7,000 rpms.

When I had it apart I checked the PV and they moved freely with absolutely no sticking.

Where should I look next? It has stock pipes with stock jetting and Tyga canisters. When it hits 7k it sounds just like a rev limiter on a 4 stroke... as if it's cutting spark or something.
Could it be a/the coils?

I had a similar problem with an NS400 a few years ago, and something that seemed to be a common problem with them. The stator windings were breaking down under load. A replacement unit sorted it out.

Check and calibrate the TPS?
A friend of mine had similar problems, turned out somebody had cooned up the TPS mechanism.
AFAIA the TPS is just a pot (variable resistor). I assume checking it involves disconnecting the plug and checking the resistance at closed and open throttle positions.
Can someone confirm this theory and have information on what the resistance should be?

drank5 wrote:
I heat cycled it 5 times using 30:1 premix with Motul 710 and avgas.

Any reason why you'd be using AVGAS? Jetting's probably way out for a start. (No jetting discussion in the public forum please.)

Do the RC Valve setup test. Details all over the forum and on the Main Site. If the Valves don't cycle then start looking at the RC servo, the TPS and the PGM. Having spare parts, or better yet a working bike, to swap your parts onto is the best way to go, especially if the PGM is up the duff! You don't want to fit a good one to your bike in case you kill it, else you'll be looking for two!

Put a meter on the battery. IGN off should obviously show 12+ volts. At idle around 14.2V. Rev the bike and you shouldn't see much variation. Spikes and/or dips would suggest the reg/rec. When I had a reg/rec fail I found the usable RPM dropped, and dropped quite rapidly!

As Middo already mentioned, a stator failing can cause those symptoms too. I had a stator fail on my MC21 many years ago when a pulse coil allen bolt decided to work loose and flick in behind the flywheel, which caused to coils to eventually short. Although the motor stopped abruptly (as the pulse coil dropped out of position and I lost spark) I made the terrible assumption that the bolt had fallen out of the holes in the bottom of the flywheel cover! Over time, as the stator windings burnt out more and more, performance of course degraded. I took the stator to our local power tool repair shop who rewound it for me. I was in the hire/rental trade then, so it was far cheaper for me than going to a bike shop!

I'd start off by putting 97/98 octane fuel in it, adjusting the oil ratio (30:1 is way oil-rich for most applications) and checking the jetting is suitable for the state of tune. It's all speculation when you've not even said if it's a stock bike or not!
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bike is 100% stock other than tyga canisters.

I checked the RC valves and they are properly tuned and the servo works as it should according to the manual.

I'll check the battery, but it's brand new.

I guess I'll search the manual or the forum on how to check TPS.

I do have a 28 that I can swap some parts on if need be. I swapped the coils and that didn't do it.

bike is now running on the oil pump again.

so since my last post I've checked several more things

-the wire splice has not been done, so the bike is 100% stock sans the Tyga aluminum canisters
-I checked the voltage and it was rock steady at 12.5 idle and 14.2 rev'd up- it even held steady while bumping the 7k mark which it won't go past
-checked pickups on flywheel for loose solder joints.
-checked the pick up wires all the way back to the PGM
-cleaned many connectors
-unplugged the PV and manually put them on hi/low with no results
-swapped rectifier and no change

I guess I'll track down a PGM and see if it will do the trick