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Post by torinoman on Jul 11, 2024 8:43:03 GMT -5
Hey Group! Once again, I'm here seeking your infinite wisdom. This is something super easy I'm just missing somewhere.
Current build is a 2001 pre-bug, 70cc tops black trophy, 17.5 dellorto, boyesen reeds, leo vince tt, 13/44 gears, tops variator kit, 6.5g dr pulley rollers, polini speed 3 clutch and bell (adjustable spring tension), and 1500 rpm malossi contra.
So, here's what I'm dealing with. From a standing idle start to wide open launch, the rpm's start off good (I think) at approximately 8500-8800, then spike to 9300, then decrease back to the starting rpm in the mid to upper 8's until 40mph or so and increase normally from there. This rpm spike and recovery all happens in a matter of a few seconds. Clutch engagement point is around 6k. No evidence of belt slippage.
First question- Is this even the rpm range I need to be in for this build?
Second question- How do I work out the rpm spike or am I being too picky?
Seems like I need heavier rollers to make it shift out faster, but I don't want the engine to fall out of the power band. Plus the belt already starts to move in the pulley a little before the clutch engages and I believe heavier rollers will amplify that taking away my lowest gear ratio.
Thanks in advance!
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Post by billwill on Jul 12, 2024 6:46:54 GMT -5
That spike and then drop of the RPMs is likely due to the rear pulley and something that is common with stock rear pulleys. It is caused by the non-linear ramps or guides and the way the sheaves open. There's no way to avoid this without going to an aftermarket rear pulley with linear guides like an overrange. Beware if you do go overrange, you'll have to grind down/remove material from the inside of the case to get it to fit. Ask me how I know lol. It's not super complicated but it requires some work.
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Post by torinoman on Jul 12, 2024 7:19:26 GMT -5
That does make sense now that you mention it. I had actually thought about that, but dismissed the idea because the spike happens so early. I'm talking about less than a second after going wide open. Does the torque driver open that fast?
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Post by Zino on Jul 12, 2024 11:47:23 GMT -5
the torque driver does open that fast as soon as you hit the throttle the weights throw out upshifting and pull the bet down in the back pulley to open the torque driver
you have a dog leg in your torque driver
how it works is the dog leg holds your rpm high and then they shift into a over drive gear and then you rise from there to your top speed .
When you have a stock engine this dog leg makes up for the lack of power
when you add power it gets very noticeable you feel the up down in rpms .
just buy a straight groove torque driver and you will have to reset the weights in your variator and you will have smooth shifting all the way up
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Post by torinoman on Jul 12, 2024 12:13:39 GMT -5
the torque driver does open that fast as soon as you hit the throttle the weights throw out upshifting and pull the bet down in the back pulley to open the torque driver you have a dog leg in your torque driver how it works is the dog leg holds your rpm high and then they shift into a over drive gear and then you rise from there to your top speed . When you have a stock engine this dog leg makes up for the lack of power when you add power it gets very noticeable you feel the up down in rpms . just buy a straight groove torque driver and you will have to reset the weights in your variator and you will have smooth shifting all the way up That sounds like what is happening. I understand the concept and how they work with the slots and angles, just didn't think it shifted that fast. That's why I asked the group! As far clutch spring adjustment, should I go stiffer to try to match the rpm spike or leave that alone? Keeping in mind this is a daily rider. I don't want to have to rev it to the moon to get it to move! Luckily my powerband is wide enough I really don't feel the rpm shift much. So far, there doesn't seem to be many options for a pre-bug pulley. Kind of weird. I'll keep looking for one though. What are your thoughts on the RPM range I'm working in? My butt Dyno doesn't work right all the time! Thanks Zino, I always appreciate you and everyone else's insight! |
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Post by Zino on Jul 12, 2024 14:00:10 GMT -5
the pre bug uses the same pulley as the bugeye pulley
ncy makes one that will fit so does malossi and polini
the 2008-2011 bugeye stock pulley is straight groove
leave the clutch springs alone your launch sounds mind just your shift is magnified .
On my daily drivers the vinos with akit and street pipe with a wide power band
I run the stock dog leg rears
I just power through the shift and get the benefit of the lowered rpms at cruising speeds
On the narrow power band set ups changing the torque driver is a must do!
Because every time you come off the throttle the dog leg pulls you out of the power band and your on off throttle response would suck
On the na
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Post by torinoman on Jul 12, 2024 14:04:13 GMT -5
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Post by Zino on Jul 12, 2024 14:19:21 GMT -5
after looking at partzilla parts for pre bug Zuma ,vinos ,jogs and bug eyes
I may be wrong about the 99 -01 pulley being the same as the other Zuma pulleys .
I have not worked on a Zuma in a couple years .
post up some measurements just to verify with the other bug eye Zuma guys on here
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Post by Zino on Jul 12, 2024 14:37:39 GMT -5
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Post by torinoman on Jul 12, 2024 15:04:14 GMT -5
I'll keep digging and update if I find anything. Options seem to be very limited. I'm definitely curious to know the difference between the prebugs and the bugs. The NCY sliding half that I see everywhere says it won't work on a prebug unless you have the bugeye other half.
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Post by Zino on Jul 12, 2024 15:16:50 GMT -5
the 2002 -2005 pulley for the Zuma was different than the 2008-2011 Zuma pulleys so I had to order the whole assembly .
the 2008 has the straight groove the 2005 had a dog leg
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Post by torinoman on Jul 12, 2024 15:40:46 GMT -5
It may get to point of cost vs. reward!
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Post by Zino on Jul 12, 2024 20:00:25 GMT -5
For a daily driver I would not bother
for a race build you would need it
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Post by torinoman on Jul 12, 2024 20:32:28 GMT -5
Now I'm thinking about going lighter on the rollers. That might slow the shifting a bit?
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Post by torinoman on Jul 17, 2024 15:26:32 GMT -5
Still haven't been able to track down a rear pulley. I've ordered the NCY part# 1200-1250 from 3 different vendors only to find it sold out and backordered everywhere. I can't believe it's this difficult to find a straight groove torque driver for a prebug.
Any ideas on an adjustment that might soften the rpm shift a bit? I tried lighter rollers, that just made it worse and put it into too high of an rpm range. It appears I'm going to have to make the best out of this stock pulley. I'm just not in a position to dish out $250+ for Malossi stuff. I'm really not even sure if it's available anyway!
I watched Brent's budget overange pulley videos and got to thinking about trying a GY6 pulley or something else unconventional.
I'm open to suggestions guys.
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