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Joined: Mon Mar 27, 2017 6:33 pm
Posts: 2
Hello all,

I have decided to take the plunge and upgrade my 2001 Prebug to a BBK. The weather is finally getting nicer here and I want to get my scooter on the road in the next month or so.

I bought the scooter last fall and it was running but stalling often when I got it. It was completely stock with 12000km on it. Over the fall / winter I cleaned her up as best as I could and replaced a couple things ( CF Reeds, new fuel and oil lines, spark plug, battery and tires. ). I checked the compression last fall and it was reading around 95 psi.

I cleaned the carb and replaced the float and needle valve set. ( Someone previously used a nail for the dowel pin which was rusted ). A couple weeks ago I fired it up again but I was getting a constant leak from the overflow pipe which I could not figure out why. The needle seat was as clean as can be and the gasket was in good condition. From what I could tell the float was not floating at the right point to close the valve which I can not adjust. It measured the correct height parallel to the gasket surface.

Anyways, I don't really want to mess around with that carb anymore. I have some parts in mind but I had some confusion over the jets I should purchase and a couple other things.

My build list so far is:
Cylinder - Top Trophy Black 70cc
Carb - Polini CP 19-21mm ( Not sure which they are the same price.) I was going to buy regular Dellorto but they are not in stock from the place I am buying.
Intake - Intake System Doppler S2R (23mm)

I am running a stock pipe on this scoot. Which range of main jets should I start with I was thinking 95 with the 19mm or 105 with the 21mm? I live in Vancouver, BC not far above sea level. Also should I replace the top end bearing while I am at it? If so which size would the be I cant seem to find that information.

Thanks, any advice is appreciated. I am pretty new to tuning but trying to learn what I can.

Sun May 07, 2017 1:34 pm
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Joined: Mon Jul 02, 2012 10:08 pm
Posts: 1123
scooters and mods: Tp 70cc,next r,vforce 3 reed block,s6 variator,stock carb 86 mj,vee rubber 119c tires,med contra,stiff clutch springs
Post Re: 2001 Prebug Build Advice
Yes 100% change the small end bearing. You want a 10x14x13, and don't cheap out buy a good one. That bearing gets the most abuse very important to change it.

Now for the jet size.

With a prebug if you just change the reed valve to an aftermarket one and reuse the intake elbow you might be able to make the stock air box work. With that SR2 I'm about 99% sure you'll need a different air filter. I have the Stage6 big valve intake and have to use an open style filter. Now the polini cp carb says it uses PWK jets I wonder if the slides are like a pwk also? If so the stock throttle and cable will not work. Long story short buy this and save yourself a big headache ... -21mm.html
Anyway with an open style filter you'll need bigger pilot and main jets. I've never ran a dell with an open filter but I'd guess between 100-110 with your combo of parts. I'm running a 28mm PWK on my prebug with an open filter and it has a 52 pilot and a 142 main jet. Now you can't compare those numbers as a dell and PWK are completely different. I'd buy one of those aftermarket air filters that have a housing around them. It will make way easier to keep it in tune and let you run a much smaller main jet saving on fuel.

2010 Zuma
L/C S6 R/T 95, S6 R/T 44/90 crank, S6 95cc Big Bore Pipe,Trenched and Ported Cases, MVT DD19 Iggy, MXS Intake with KX 85 Reeds, Malossi Overrange , Keihin PWK 35mm carb, UNI air filter, Doppler 14/42, Dr.Pulley HIT Clutch ( 8000 rpm engagement ), Stage6 433 R/T clutch bell, Premix 32-1.

2001 Zuma (Pre-Bug)
MXS Race 70cc, 28mm PWK , S6 Big Valve, SR-1 Crank, S6 R1400 Pipe, Malossi Overrange

Sun May 07, 2017 2:14 pm
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Joined: Wed Mar 25, 2015 11:44 pm
Posts: 124
Location: East Bay CA
Post Re: 2001 Prebug Build Advice
To go along with that setup I would also recommend a pipe for that setup your brewing up. I have a doppler s3r exhaust (derestricted) I would let go for cheap if your interested.

1990 Yamaha Jog CG50-CW50 swap
1992 Yamaha Jog CY50-stock
2000 Honda Elite SR50-72cc Corsa, Arrow, OKO24, Polini vari, 8.4:1
1995 Suzuki Intruder VS800
2014 Yamaha FZ-09

Sun Jun 04, 2017 2:24 am

Joined: Fri Mar 02, 2018 6:21 am
Posts: 19
scooters and mods: 2002 prebug (Canadian) stock
Post Re: 2001 Prebug Build Advice
Did you get this build going over the winter? Just wondering what setup you decided to go with

Giannelli extra exhaust, 98 main jet, 1500rpm clutch springs, 2000rpm contra, 5g rollers, carbon reeds

Fri Mar 09, 2018 4:14 am
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