CR33's running rich.....help

[Spamwood]

I have open CR33's with 125 main jets on my GS1000  which has a standard engine and a good free flowing exhaust 

 The bike has been on the dyno and the fuelling is showing very rich,   Plugs and the end of the exhaust are rather black, horsepower output is a fairly healthy 83 for a standard engine 

 When we reduce main jet size the fuelling looks right on the dyno but looses 10/15% power.

 Can anyone give any advice on how to lean the mixture and retain the horsepower ?

 I should at this point say that I am mechanically inept  so would appreciate any help you can give 

[Gixer1460]

AFR - looks right..... or IS right? Without seeing the dyno graph with AFR plotted, its tricky to advise, but 10-15% is a lot to lose with a jet change - they do go up and down in 2 point changes, not just 5 or 10 points. If it's properly rich, ie. less than 12 : 1 AFR then its not max power - that should be around 13.2 : 1 AFR. Is the ignition system correct and tip top? likewise the valve clearances?

[nlovien]

good suggestions  - yi get unusual results with carbs - check yir ignition - not so much the timing but the strength of it - corroded connectors, weak coils - running the ignition power feed via the switch gear  - plug gaps out etc... - TBH if there's any part of this circuit that's original GS then it will be needing TLC 

[Dave61]

I`ve got the exact same problem with my Keihin CR33`s, carbs were supplied by Steve Walls from Gremlin Racetech & he swore by them, they`ve only done around 110 miles since being fitted & as I stupidly left them with fuel in I`ve had them apart a coupe of times to to make sure they`re absolutely spotless but has made no difference. Thinking of replacing with Mikuni 36`s as they seem to be a bit less temperamental.

Bike is a 79 GS1000EN with 1100 Wiseco kit, Fast Road Cams, Crank by Chris Applebee & Head by Nick Stratton.

 

[GarinRogers]

On 6/14/2018 at 6:48 PM, Dave61 said:

I`ve got the exact same problem with my Keihin CR33`s, carbs were supplied by Steve Walls from Gremlin Racetech & he swore by them, they`ve only done around 110 miles since being fitted & as I stupidly left them with fuel in I`ve had them apart a coupe of times to to make sure they`re absolutely spotless but has made no difference. Thinking of replacing with Mikuni 36`s as they seem to be a bit less temperamental.

Bike is a 79 GS1000EN with 1100 Wiseco kit, Fast Road Cams, Crank by Chris Applebee & Head by Nick Stratton.

 

Nice GS what exhaust system is that ? 

 

[Dave61]

Hi Garin,

It`s Stainless Bandit down pipes with a homemade link pipe to a Scorpion can I bought at the NEC Bike Show around 2008, I tried looking at getting another one recently but had no joy.

Cheers

Dave

[GarinRogers]

38 minutes ago, Dave61 said:

Hi Garin,

It`s Stainless Bandit down pipes with a homemade link pipe to a Scorpion can I bought at the NEC Bike Show around 2008, I tried looking at getting another one recently but had no joy.

Cheers

Dave

Thanks Dave, never mind they look good !  Rumour has it that a stainless version of the Harris works collection is in development, by the time i get mine back together it might be available.

 

[BigT]

Spamwood, I think the problem is that the 33s are just too big for a stock motor. You'd be better off going back to a VM 28 with similar jetting, The 33s are flowing almost 50% more air