MC28 running fault,help required

**Fri Jul 10, 2009 7:41 am » Post: #1 » Download Post**

Gentlemen,

my 28 sp with 7700kms and standard spec, will not idle,it starts and runs very unevenly,seems to run much colder on frt cylinder.I have swapped plugs,coils,pgm box,done compression check,cleaned carbs,replaced needle valves.None of the checks have made any difference.The bike runs fine at higher rpm,but stalls if you let the revs drop.Can anyone help please.
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MC28 ROTHMANS SP
MC28 SE R2T
TZR 3XV9 RS
TZR 3XV4 R
RGV250M
RS250 HARADA
CBR400 NC29
VFR800FIY
CB1000 BIG ONE
ZOOMER 50
MB5
749R
ZX7R P6
FZR400RRSP 3TJ2
YZF750R
GSXR750WT

**Fri Jul 10, 2009 11:04 am » Post: #2 » Download Post**

Will it idle with full choke on?

Have you checked the air screw setting?
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

**Fri Jul 10, 2009 11:25 am » Post: #3 » Download Post**

Dave,

with full choke it will just about idle,but very eratic,self revs up and down from 1000-2500rpm.
_________________
MC28 ROTHMANS SP
MC28 SE R2T
TZR 3XV9 RS
TZR 3XV4 R
RGV250M
RS250 HARADA
CBR400 NC29
VFR800FIY
CB1000 BIG ONE
ZOOMER 50
MB5
749R
ZX7R P6
FZR400RRSP 3TJ2
YZF750R
GSXR750WT

**Sat Jul 11, 2009 3:03 pm » Post: #4 » Download Post**

Might be the crank seals,do a search about how to check them.

**Mon Jul 13, 2009 11:48 am » Post: #5 » Download Post**

When you cleaned the carbs, did you ultrasonically clean them?

I had a similar problem on an RGV many years ago and standard cleaners didnt sort it but the ultrasonic bath did.

**Mon Jul 13, 2009 6:36 pm » Post: #6 » Download Post**

veroli1994 wrote:Dave,

with full choke it will just about idle,but very eratic,self revs up and down from 1000-2500rpm.

Sounds to me like you have an air leak somewhere then, and the choke is just about able to richen the mixture up enough to run.

Check very carefully all the seals between the carbs and the reed blocks, then the reed blocks and the crankcase.
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

**Tue Jul 14, 2009 7:34 am » Post: #7 » Download Post**

Thanks for the advice,tonight I shall look further into it,I am fearing the worst as bike has been sitting around unused.

mike
_________________
MC28 ROTHMANS SP
MC28 SE R2T
TZR 3XV9 RS
TZR 3XV4 R
RGV250M
RS250 HARADA
CBR400 NC29
VFR800FIY
CB1000 BIG ONE
ZOOMER 50
MB5
749R
ZX7R P6
FZR400RRSP 3TJ2
YZF750R
GSXR750WT