|
|
Post by alentje on Jun 24, 2015 3:55:50 GMT -5
Hi guys. I did a complete rebuild yesterday and i am going to start it soon. I wondered what jet as maximum would i need with a 12mm carb and open air filter? My setup is as following:
- Athena 50cc aluminum kit
- 12mm Gurtner carb
- Polini upgear kit
- Malossi yellow clutch springs + Stage 6 medium contra spring
- LeoVince ZX
- Malossi carbon reed block
- Stage 6 Sport PRO variator w/ 6g rollers
- Athena belt
Jet with my exhaust should be 82, how much sizes up do you reckon for an open filter?
Thanks
|
|
|
|
Post by 90GTVert on Jun 24, 2015 16:17:31 GMT -5
SOmething like 20-25% increase may work for an open filter. That's what seemed to work on my Minarelli airbox vs UNI filter anyway. So my guess would be roughly 100-105 for the main jet.
|
|
|
|
Post by Elektrey on Jun 24, 2015 18:04:31 GMT -5
start from like 105 and work your way down. check the plug color each time and look for any rough spots in the throttle.
|
|
|
|
Post by spaz12 on Jun 24, 2015 18:29:44 GMT -5
|
|
|
|
Post by alentje on Jun 25, 2015 16:32:30 GMT -5
I know they don't improve performance but the sound is amazing. I have a 90 jet in here, will it do any harm to the engine? I have tried 92,95 but not 98. Both 92 and 95 give the same sluggish throttle response. I think i'll stick to my factory airbox
|
|
|
|
Post by spaz12 on Jun 25, 2015 18:01:11 GMT -5
The sound is pretty cool I guess. Sorta like having two pipes.
Yes, they can damage your engine. But so will an improperly tuned carb with a regular air box. If you jet it right it will work. The problem is that they are hard to jet for most people. AND of course, the no benefit thingy.
|
|
|
|
Post by Sitticuss on Jun 26, 2015 15:48:40 GMT -5
The sound is pretty cool I guess. Sorta like having two pipes. Yes, they can damage your engine. But so will an improperly tuned carb with a regular air box. If you jet it right it will work. The problem is that they are hard to jet for most people. AND of course, the no benefit thingy. The benefit is the AWESOME sound... |
|
|
|
Post by spaz12 on Jun 26, 2015 15:52:05 GMT -5
True. I run an open filter and love the sound. Until there's a cop around, then not so much.
|
|
|
|
Post by alentje on Jun 30, 2015 11:34:35 GMT -5
Lol no cop will touch you ever for that here.
So i've tried a 98 jet yesterday and it looks like it's almost the same if not worse. Do you think a 12mm carb is small for my setup? Or maybe i could go back to my stock airbox and start from there. The problem is that the throttle response is not direct, there is a 1 second delay which makes me mad when taking off at traffic lights.
Also, when i'm going up a pretty steep hill it loses power at full throttle and kind of bogs down.
|
|
|
|
Post by birdman on Jun 30, 2015 17:46:01 GMT -5
jetting issues will make you want to pull your hair out, sell your scoot, and run away lol. I feel like im on the cusp of getting my engine tuned properly. but it will have to wait until october now..
|
|
|
|
Post by birdman on Jun 30, 2015 17:46:57 GMT -5
go with a stock airbox or a dual layer foam filter.
|
|
|
|
Post by fe53series3 on Jul 1, 2015 17:59:50 GMT -5
Lol no cop will touch you ever for that here. So i've tried a 98 jet yesterday and it looks like it's almost the same if not worse. Do you think a 12mm carb is small for my setup? Or maybe i could go back to my stock airbox and start from there. The problem is that the throttle response is not direct, there is a 1 second delay which makes me mad when taking off at traffic lights. Also, when i'm going up a pretty steep hill it loses power at full throttle and kind of bogs down. Your 12mm carb is always going to hold you back. The kit that you've fitted is very interesting, but if your motor could speak, it would be crying out for more fuel and air. I would respectfully suggest that...... everything you've fitted, would be based around 'increased power output'. This can only be delivered by removing the 12mm Gurtner carb, and fitting something more commensurate with your objectives. This would require the replacement of the inlet manifold, with one that matches (say) to the Dellorto range. If you like the idea of tuning..... the PHBN would be highly suitable.... 17.5 would work well, and produce a significant increase in power output, without being too large to waste fuel down the throat. You could go to PHBG say 19....... but with less tuning options...... and anyway, bigger is not always better. If you do increase the carb size, don't forget to check your air inlet diameter..... that's the smallest diameter in your air-inlet system. The smallest air-inlet diameter (area = Pi r sq) should be at least a third larger than the area of the carb outlet throat. Obviously, if your air inlet is smaller, your bigger carb will not function correctly. After dumping the 12mm Gurtner, for a PHBN 16, my scoot was totally throttled. I modded the airbox ducting, and drilled extra holes filter side, to gain more area than the carb throat. ..... it flew, thereafter! Modding the fuel/air supply should be high up on your agenda.  |
|
|
|
Post by alentje on Jul 3, 2015 17:58:41 GMT -5
Oh thanks mate, i'm going to get a 17.5 soon!
|
|
|
|
Post by alentje on Jul 3, 2015 18:00:07 GMT -5
Lol no cop will touch you ever for that here. So i've tried a 98 jet yesterday and it looks like it's almost the same if not worse. Do you think a 12mm carb is small for my setup? Or maybe i could go back to my stock airbox and start from there. The problem is that the throttle response is not direct, there is a 1 second delay which makes me mad when taking off at traffic lights. Also, when i'm going up a pretty steep hill it loses power at full throttle and kind of bogs down. Your 12mm carb is always going to hold you back. The kit that you've fitted is very interesting, but if your motor could speak, it would be crying out for more fuel and air. I would respectfully suggest that...... everything you've fitted, would be based around 'increased power output'. This can only be delivered by removing the 12mm Gurtner carb, and fitting something more commensurate with your objectives. This would require the replacement of the inlet manifold, with one that matches (say) to the Dellorto range. If you like the idea of tuning..... the PHBN would be highly suitable.... 17.5 would work well, and produce a significant increase in power output, without being too large to waste fuel down the throat. You could go to PHBG say 19....... but with less tuning options...... and anyway, bigger is not always better. If you do increase the carb size, don't forget to check your air inlet diameter..... that's the smallest diameter in your air-inlet system. The smallest air-inlet diameter (area = Pi r sq) should be at least a third larger than the area of the carb outlet throat. Obviously, if your air inlet is smaller, your bigger carb will not function correctly. After dumping the 12mm Gurtner, for a PHBN 16, my scoot was totally throttled. I modded the airbox ducting, and drilled extra holes filter side, to gain more area than the carb throat. ..... it flew, thereafter! Modding the fuel/air supply should be high up on your agenda. My speedfight goes arround 85/90 km/h with a worn belt and this carb, will it go any better with a 17,5? |
|
|
|
Post by alentje on Jul 4, 2015 12:19:56 GMT -5
Ouch, i replaced everything except fot my cylinder, as many mechanics told that it is ok. The conpression now is just shy of 7 bar (6.8). What is more funny is the fact that i have a brand new unused cylinder and mahle piston, both pulled from a old peugeot engine that wasnt even started.
|
|
