RC 45 'quick throttle' modification

[LotusSevenMan]

I have read a bit about using an RC 45 throttle to give more throttle opening with less movement of the wrist. Thought I'd give it a go.

Well, I now have an RC 45 throttle grip (Thanks Mr Paul 'Tempest'............ No, not Troys brother).

Thought I'd do some dimension checks before fitting etc.
OK, here goes. All dimensions in mm.

Outer diameter of twist grip tube
Std 25.44
RC45 25.77

Inner dia of tube
std 22.54
RC45 22.47

Diameter of circular body that
the throttle cable wraps around
Std 32.00
RC45 33.73

In effect using Pi etc that means an effective circumference difference of approx 5.4mm.

I have read of complaints about excessive end float (in and out along the bar). This is due to the thickness of the end section (where the two cables attach) being 2.3mm less on the RC45 than the std one.
Now if you use the conventional grips then this might feel rather odd. but I have to file away retension flange to allow my heated grip to fit. It may well be that with the grip 2.3 mm further onto the throttle tube it prevents this endfloat by touching the housing without causing drag; or I might have to form a 2.3mm shim. This could be formed from cutting down the original twistgrip end section to act as this shim or a suitable washer.

We'll have to see. I'll report back when I've fitted it all.

See:- RC 45 to the right



and RC45 to the bottom.

[Stratman]

using Pi

Mmmm, Pi

[Squiffythewombat]

This might be a blonde moment but how would an effective 5mm difference produce a noticable degree change for the wrist?

[sirch345]

This might be a blonde moment but how would an effective 5mm difference produce a noticable degree change for the wrist?

The difference in relation to the RC45 throttle body and the standard item will be to do with the circumference, not the difference in diameter, IE Although the diameter difference may only be small, there will be a bigger difference in the circumference, hence the quicker opening of the carbs with less turning of the throttle.

[LotusSevenMan]

I gave the diameters of the tube section more to show that the 'sloppy feel' some complain of is not in the tube itself but is the endfloat etc. & it is that makes it feel sloppy.

[LotusSevenMan]

OK.
Finally found my nylon washers that are used to space Caterham Seven suspension components. I have used two (like the one shown in the left of the pic) and cut one just fractionally larger than the twist grips outer diameter and glued that in place. Easier for me as I had to remove the grip retaining flange for the heated grip to fit correctly. Not a lot of problems to cut it the correct size then a cut across it to fit it beyond the flange is you need to. The second one was cut with a 22mm hole to allow it to fit on the clip-on tube OK and again glued in place.
Result is an RC 45 grip that now is 0.39mm less wide than the std FireStorm grip. This should mean basically no endfloat/slop!!!
RC 45 shown at the bottom.

[sirch345]

That looks good LSM

I wonder what the idea was for the extra end float in the first place

I look forward to hearing your opinion on it when the weather permits

Chris.

[LotusSevenMan]

I could only assume they had a slimmer throttle cable housing but apart from that

I'm looking forward to some good weather too. Even dry would be nice in my open air workshop!!!!

OK Today 7-1-07.
Fitted the quick throttle RC45 twistgrip today. A little bit fiddly etc but all went together fine. I wish I taken a degree angle with the original set up, but I can state that with this RC45 grip it takes 65* from fully shut to fully open. I think that is a fair bit better than std. Anyone confirm?

[Squiffythewombat]

This might be a blonde moment but how would an effective 5mm difference produce a noticable degree change for the wrist?

The difference in relation to the RC45 throttle body and the standard item will be to do with the circumference, not the difference in diameter, IE Although the diameter difference may only be small, there will be a bigger difference in the circumference, hence the quicker opening of the carbs with less turning of the throttle.

arhhhhh that makes so much more sense now!

Cant wait to hear the results, i wonder if this would invalidate the "overgrip" technique for wheelies! could be intresting!

[LotusSevenMan]

Squiffy. What also might help is the fact that I have the heated grip & it is a lot larger diameter (due to the elements etc) than the std one. So, it is easy to grab a handful without much effort. Right up your (wheelie) street!!!!!