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Post by chris66 on Apr 27, 2022 18:16:28 GMT
Hello Gentlemen. I hope I find you well.
Been a while since I've posted on here although found this forum invaluable when building my 50 special, so thank you for that. I'm running a 130cc DR kit with a Simoni exhaust but retained the 19/19 Dellorto. The bike runs well on the carb but was wondering that as it runs well on 19/19 is it worth going bigger? I've been told that it's probably best to keep the 19/19 but I hoping that by going bigger I might get better performance. The top end is around 90kmph, not mad fast as I fitted a 28/69 primary drive gear combination, I wanted acceleration over top end as I ride mainly in town and need to keep up with cars getting away from traffic lights. If I should go bigger, say a 22mm or 24mm carb what kind of performance should I expect? Or do I just reduce the chance of holeing the piston?
Thanks in advance.
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Post by tzsteve on Apr 27, 2022 19:59:20 GMT
28/69 is quite a high ratio
24 mm carb would be a nice little extra
And probably a slightly lower ratio would give more acceleration and more use of 4th gear
Or keep the 28/69 and fit a different tree
You can find a 15 bhp tree on fleabay. A 10,14,18,21 tree would probably go well with the 28/69 gears
Im currently using 29/69 with 10,14,18,20 and a 48 tooth 4th loose gear. But thats with 17bhp at 8750 rpm
My engine would not be able to pull the gearing you are currently using
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Post by chris66 on Apr 28, 2022 9:30:02 GMT
28/69 is quite a high ratio 24 mm carb would be a nice little extra And probably a slightly lower ratio would give more acceleration and more use of 4th gear Or keep the 28/69 and fit a different tree You can find a 15 bhp tree on fleabay. A 10,14,18,21 tree would probably go well with the 28/69 gears Im currently using 28/69 with 10,14,18,20 and a 48 tooth 4th loose gear. But thats with 17bhp at 8750 rpm My engine would not be able to pull the gearing you are currently using That's great advice. It looks like I will opt for a 24mm carb, don't know what to get yet. Not sure what the tree ratio is, I bought a new one when I revised the engine so it's probably the standard ratio. When I ordered the primary drive that got back to me to ask if I wanted top end or acceleration, I went for acceleration. I'm not planning on splitting the engine just yet but from what you've advised I think I should seriously look at changing the ratios. What sort of performance are you getting with your set up?... That might encourage me to split the engine again to get it sorted sooner rather than later. |
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Post by tzsteve on Apr 28, 2022 10:48:31 GMT
Top gear peak is at about 68mph on the dyno
Thats a 56 quatrinni rotary inlet mildly tuned,
28 mm dellorto
Vmc ignition
Franz pipe
Gearing is 29/69, With 10,14,18,20 tree and 48 tooth loose gear.
Hartz4 clutch
It does have a lumpy patch in the jetting at about
3000 to 3500rpm
I dont nail it very often as it can get a bit wobbly and shows signs of the frame flexing at anything over 65,
It could be made quicker but maintenance would become more of an issue
Twice the power is four times the ware and tare
Check scooterhelp.com for the gearing calculator and print out the most relevant pages
A 21 tooth tree would give a top ratio of 5.39 you have 5.15 at the moment so the swap would lower the top by about 4.6%
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Post by chris66 on May 9, 2022 17:51:44 GMT
Top gear peak is at about 68mph on the dyno Thats a 56 quatrinni rotary inlet mildly tuned, 28 mm dellorto Vmc ignition Franz pipe Gearing is 29/69, With 10,14,18,20 tree and 48 tooth loose gear. Hartz4 clutch It does have a lumpy patch in the jetting at about 3000 to 3500rpm I dont nail it very often as it can get a bit wobbly and shows signs of the frame flexing at anything over 65, It could be made quicker but maintenance would become more of an issue Twice the power is four times the ware and tare Check scooterhelp.com for the gearing calculator and print out the most relevant pages A 21 tooth tree would give a top ratio of 5.39 you have 5.15 at the moment so the swap would lower the top by about 4.6% Again thank you for your help. I'm still running the cilinder and piston in at the moment so will get on the job with the gearing once I'm satisfied that it's all run in. |
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