MC21 carb problems

**Sat Mar 04, 2006 8:03 pm » Post: #1 » Download Post**

Hi I have an MC21 and am struggling with a major flat spot at 4000-5500rpm all jets are standard air screw setting standard. Please help I'm begging to lose it

**Sat Mar 04, 2006 8:14 pm » Post: #2 » Download Post**

Mine turned out to be crank seals.
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Andy.
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**Sat Mar 04, 2006 8:39 pm » Post: #3 » Download Post**

can't be the crank seals as there only 150 miles old

**Sat Mar 04, 2006 8:44 pm » Post: #4 » Download Post**

are they in right ?

**Sat Mar 04, 2006 8:46 pm » Post: #5 » Download Post**

yes properly sat in groves

**Sat Mar 04, 2006 8:48 pm » Post: #6 » Download Post**

are the crank cases sealed ok ?

**Sat Mar 04, 2006 9:06 pm » Post: #7 » Download Post**

yes crank cases sealed properly with kawasaki three bond when I put new crank in

**Sat Mar 04, 2006 9:14 pm » Post: #8 » Download Post**

Check the TPS connector as this can make them hicup very badly at around these RPM's

Did it do it before you rebuilt the engine? Has it just started over night or slowly get worse over time?
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If I have to take the carbs off once more...

**Sat Mar 04, 2006 9:14 pm » Post: #9 » Download Post**

also should have said that the bike pulls really well when you get past the flat spot

**Sat Mar 04, 2006 9:20 pm » Post: #10 » Download Post**

don't want to sound thick but whats the TPS connector. Also problem was not there when I first got the bike running as I had drilled out pilot jets but this made the bike not want to pull higher in the rev range (flooding) this is better now with new jets. Not sure what bike was like before rebuild as it was a non runner

**Sat Mar 04, 2006 9:26 pm » Post: #11 » Download Post**

The TPS is the Throttle Posistion Sensor, its mounted on the right hand side of the carbs and has a clear/white-ish 3 pin connector just under the frame brace infront of the carbs.

If the bike is running stock jetting with any kind of air box mods or exhaust then you need to have a play with the jetting as this can cause simular probs as to what you are having on WOT. Im guessing the bike pulls fine as long as youre not on WOT
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If I have to take the carbs off once more...

**Sat Mar 04, 2006 9:31 pm » Post: #12 » Download Post**

bike is all completely standard apart from derestriction by the wiring splices orange and blue wire and GPS don't understand what you mean by WOT

**Sat Mar 04, 2006 9:34 pm » Post: #13 » Download Post**

Wide Open Throttle.
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If I have to take the carbs off once more...

**Mon Mar 06, 2006 8:52 am » Post: #14 » Download Post**

thanks for help help with this put a set of 38 slow jets in that had been slightly drilled runs perfectly now so going to get some 40's and some 42's off apex. Only thing I can put this down to is non standard air filter got some foam from local bike shop and cut my own

**Mon Mar 06, 2006 10:21 am » Post: #15 » Download Post**

Another NSR back to it's best! Wink

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