'99 Prebug Zuma Build

[billwill]

Slapped a polini sport cylinder and cheap knockoff dellorto PHBG 21 carb on the other day. 

I know I’m pushing it with the 10mm wrist pin but I’m going to detune until I can split the cases and run a new crank. We’ll see how the carb does but for $27, it was worth the gamble. 

Still running oil injection too. Not ideal but for now I’m not stressing it. 

It definitely pulls with more torque and I can tell it has more power but it’s nowhere near tuned correctly, especially the transmission. I never got the stage6 over range dialed in but wasn’t pressed on it until at least getting the new cylinder on. I upped the weights to a total of 40g and that felt better but I have a set of 7g rollers for a total of 42g that I think will do the trick for now. 

For now top speed is sitting at 42mph which is about identical to stock. Belt travel leaves a bit left to be desired so I know it has legs in terms of top speed with something other than more rpm. 

Also, who knows why but stage6 sends a pink/extra soft torque spring with the kit. I’m sure this is too soft. I have a hard spring from my other build that I’m going to throw on too and see how that does. 

[classacted]

I like those carbs with the cable going straight to the piston. no diaphram. AND cable choke. nice.

let's hope that carb does everything you want from it.

[bigmatthew86]

I wouldn’t worry about the crank at all. I put several thousand miles on stock cranks & kits on 2 different zumas. Stay around 10000 rpm, jet it right, & use good oil. I wouldn’t ditch the oil injection or electric start unless you’re going all out race build. I don’t think the gain is worth the loss of convenience personally. My last Zuma (bug eye) with a street race 70, dell 17.5, Yasuni r would do around 55 on the flat with my 260lbs & I could pull up to the pump & gas it up & then use the electric start & drive off & rip at around 95-9700 rpm on a stock crank lol.

[billwill]

Aug 7, 2023 9:42:13 GMT -5 classacted said:

I like those carbs with the cable going straight to the piston. no diaphram. AND cable choke. nice.

let's hope that carb does everything you want from it.

Thanks man and haha, I was fiddling with it today and the vacuum bung or whatever fitting it’s called slipped right out when I was trying to slip the line off. Oof. I jammed it back in. That’s tomorrows problem.

[billwill]

Aug 7, 2023 12:53:32 GMT -5 bigmatthew86 said:

I wouldn’t worry about the crank at all. I put several thousand miles on stock cranks & kits on 2 different zumas. Stay around 10000 rpm, jet it right, & use good oil. I wouldn’t ditch the oil injection or electric start unless you’re going all out race build. I don’t think the gain is worth the loss of convenience personally. My last Zuma (bug eye) with a street race 70, dell 17.5, Yasuni r would do around 55 on the flat with my 260lbs & I could pull up to the pump & gas it up & then use the electric start & drive off & rip at around 95-9700 rpm on a stock crank lol.

Good to know and gives me some peace of mind! I’m just going to detune it and do like you did and keep it just shy of 10k rpm.

The convenience of throwing in pump gas and not mixing sure is great. I need to get some replacement oil feed hose because I feel like I’m stretching it right now with the new carb’s oil feed inlet.

I had to remove the electric start to fit the over range kit. That thing is massive. Been spending a fair amount of time shaving the case down for the rest of it to fit.

Polini 4 race pipe came today. Hopefully will have that on soon.

Does anyone have any recommendations on jetting with this build? Right now I am running the 21mm PHBG with a 40 pilot and 85 main. Haven’t had the time to install the CHT gauge but will soon to get an idea. Feels ok for now.

[classacted]

'the vacuum bung or whatever fitting it’s called slipped right out when I was trying to slip the line off. Oof. I jammed it back in'

I decided to eliminate the float bowl drain on one of my carbs by filling the outlet with solder and it has worked perfectly. I'll bet you can solder that part on permanently. I assume you're talking about a hose nipple.

[billwill]

Aug 8, 2023 22:32:05 GMT -5 classacted said:

'the vacuum bung or whatever fitting it’s called slipped right out when I was trying to slip the line off. Oof. I jammed it back in'

I decided to eliminate the float bowl drain on one of my carbs by filling the outlet with solder and it has worked perfectly. I'll bet you can solder that part on permanently. I assume you're talking about a hose nipple.

Yep that’s it, the hose nipple. That’s not a bad idea - is there a special type of solder to use or just electrical solder? I’m assuming not electrical solder?

[Lucass2T]

Aug 7, 2023 9:42:13 GMT -5 classacted said:

I like those carbs with the cable going straight to the piston. no diaphram.

Thats only with those silly 4poops.
Dellorto PHBG carbs are excellent for every 2t build between 5 and 15hp.
Also oem equipment op ktm dirtbikes, that says enough.

[Zino]

If you need a oil hose
I found one that works in the weedwacker section at lowes .
Its made for 2 stroke weed wackers

[classacted]

the solder I used was given to me by my brother-in-law so the origin is unknown. he said it's the best 'wire' solder he knows of. it is super thin.

[billwill]

Aug 9, 2023 7:58:11 GMT -5 Zino said:

If you need a oil hose
I found one that works in the weedwacker section at lowes .
Its made for 2 stroke weed wackers

Right on, was going to just get some fuel hose from the local auto parts store but I like this better.

[billwill]

Spent some time throwing on some new bars and stem, connecting the stage 6 mini gauge/temp sensor and 4 race pipe.

There are a LOT of cables and wires and its becoming a mess back there. You can see in the pics how bad it is but it works for now. No back brake as I needed a new brake cable and that came today from Amazon. Adelin makes some good stuff.

Replaced the front brake line and caliper while I was in there.







Will post more pics of the pipe and everything else soon but for now got it into a rideable/testable state. Clutch was engaging around 8k so turned that down a bit and now engages at 6.5-7k. I will probably tune it down a bit more so that it sits somewhere around 5.5k or so.

Current jetting with the 21mm PHBG:
- pilot: 38
- main: 85
- w16 needle: 2nd notch from top

I never gave it any good WOT runs but cylinder head temps never got above 130º c. I might just throw in a 90-95 main to see if it takes it.

Took it out and wow, that pipe sure did wake it up. it pulls hard from engagement all the way to 10k rpm. I need to be careful with the stock crank for now so I may end up running heavier rollers to keep it further below 10k. I think I am running a mix of 7g and 5g right now.

It runs like a bat out of hell all the way up to top speed but top speed right now is a very underwhelming 41mph. It may have some more in it but I didn't want to push past the 10k rpm mark much. Heavier rollers may do the trick.

I had also switched out the stage6 extra soft torque spring that came with the over range setup for a red malossi hard spring. This may be limiting top speed as well. I can either throw back in the stage 6 spring or I have an extra malossi white spring. Might start with the white spring and go from there.

[billwill]

OH and I wired up a stage 6 left side switch.. my lord this took some time to test things with a volt meter to figure out what is what. Stage 6 sends decent documentation on what each wire is for but I couldn't find anything online about the Zuma harness and what each color was for because the stage 6 harness does not match up to that of the stage 6 one.

For anyone considering this mod, hopefully below is a helpful resource. The top drawing is for the stock connector and bottom is for the SSP switch. Each drawing is looking directly into the plug with the clip at the bottom. (Slot 5, in the middle, is empty).

[billwill]

Got the Polini 4 race pipe installed and cleaned up the handlebars a bit.

Temps were fine but I wasn't able to do any WOT runs to really test. Felt like it could use more so upped the main jet to a 95. Need to take it out for a spin to see how it will take to the main jet change but its idling well and feeling good on the stand.

[billwill]

Took some time over the past few days to really get into things and tackle some odds and ends.

I had been wanting to throw the Aerox wheels on and get that started so I took the old fork/triple tree off and began to dig in. I had heard that the ball bearings can get lost and go everywhere and as careful as I was, sure enough, a few went flying. I ordered some replacement bearing sets and they should be here soon. In the meantime I've used what I have to piece it back together and mock it up.

THEN... during putting the new fork on I realized after many measurements and caliper readings that I mistakenly ordered the fork for 2002+ Aerox's and NOT pre-2002. Poop.

Basically the fork I have has a tapered steer tube where it's 30mm at the base and 27mm at the top. So it tapers out and all of the stock hardware, bearings and stem fit, but the bottom is too big. After many, many online searches, I couldn't figure out what type of bearing I needed that would fit, if ANY. I have a buddy on facebook who is going to send me an extra triple tree he has that will fit if I can't figure this out.

In the meantime, if anyone here knows of a steering bearing that will fit this fork AND the prebug headset tube, please chime in because I'm at my wit's end. For the time being to get the bike like you see it (non-ridable, but rollable), I used an old mountain bike headset bearing I had laying around that let me mock it up lol.

I had also ordered some new body panels from Brixiamoto (super cheap IMO and easy purchase on ebay) and they had been sitting around for a bit so I wanted to start to see how it would shape up. For anyone on the fence about where to get some, I was HIGHLY impressed with the quality and finish. They have some interesting colors too like cocktail, but I went with the classic blue. In hindsight, I could have taken a liking to white, but this blue with the wheels is a look I like for now.

www.ebay.com/itm/373743156859?hash=item5704d3fe7b:g:PDoAAOSwSvlgQtqs

I was thinking of (and had purchased some) doing classic Yamaha decals but after seeing how clean these panels are in this state, I'm thinking just a BW'S decal on the back sides. Below are some examples I've been thinking about and got inspiration from another guy on this forum.

For anyone interested, this site is where I found them. They have some pretty rad decals: www.motorkit.com/en/stickers/25641-sticker-kit-for-mbk-booster-yamaha-bw-s-phase-1-playing-world-white-grey-purple.html?search_query=bw%27s+sticker&results=16

I'm not doing a full disc conversion on the rear but running a drum adapter. I had done some research and talked to some people who said the rubber and wheels would fit but my lord it's tight. There is maybe 3mm (not joking, 3mm lol) of clearance between the rear wheel and the 4 race pipe. I'm going to throw some washers behind the exhaust bolts to space it out a bit.