My SP Carb Nightmare!

[TeamGSXR]

Hello stranger!

Yeah it's still going on. The damaged cast was a big set back in March. I waited to see if I could source replacement BST35's but it hasn't happened and hence the modified 33mm's.

[stripes1976]

i think i had a set of bodies i use for spares and 2 sets which i use on mine but thats about it. 35ss are hard to come by. I still got both of mine at the minute. And the 442 is going like a rocketship.

[TeamGSXR]

Carbs are off again. Hooked up with the carbtune the first carb isn't giving much of a reading on idle. I suspect it's related to the throttle valve control lever positioning. Going to measure where each butterfly sits with a vernier gauge.

By the time I get this sorted I reckon I'll have sourced some 35's!

What's the 442 putting out horse and torque wise?

[TeamGSXR]

carbs have been off and back on again today. It's actually pretty easy now

I balanced the 3 throttle valve screws on a bench measuring position with a vernier. Then ensuring they closed OK. Decent instructions in the RF600 service manual.

Once again the first carb reading was very minimal... Which looks like it's not so much of an issue? I was reading Tony Sleep's excellent web page and he mentioned on his SP he had to turn the carbtune upside down to get a reading.

One thing to note : carb vacuum is much lower on these bikes than on most, at least on the SP it is, because of the large carb diameter and small swept volume of 100cc cylinders. Conventional balancing guages should be OK but I found that with the Morgan Carbtune I used, it was necessary to use the Carbtune upside down to get a sensible reading. This is suggested in the instructions as necessary on some bikes and works fine. Right way up they barely registered a vacuum.

---

Has anyone found a Gunson colortune useful in setting the mixture?

[Variablevalves suck]

Hi J,
Ya fixed them carbs yet? used a coluortune some time ago on a KR1S and never got on with it, dyno's the way to spend ya momey.

[TeamGSXR]

Hi Chris,

Going to attempt a balance with the carbtune upside down. I think your right with regards to dyno tuning. Just not sure I can justify the cost of the tuning... RJS at Mallory last time advised it was going to be expensive and that was with the original SP spec carbs.

[Variablevalves suck]

Ye could get expensive but thinking the cost of a colourtune may buy ya a basic dyno run and if you ask the right questions you'd get enough info to get the carbs close.

[TeamGSXR]

That's true. It was £40 for a dyno run last time i went but I had to ride the bike 20 odd miles there. This time it wouldn't make it

Plan (A) Get a 2nd hand colortune on the cheap. Plan (B) Once I've had enough with a colortune in plan A I'll get it dyno'd lol. It would be nice to get a set of SP carbs though and have it setup properly with them on. Maybe if I wait a bit longer who knows what will turn up - wishful thinking perhaps