2001 Yamaha Zuma Trash to Treasure Rebuild

[billwill]

I don't know why I never started a build thread for this bike, but I purchased it almost a year ago when I found it sitting on Facebook marketplace in dire condition. It had been crashed and the front forks bent, rusted out pipe, just a mess of a bike altogether but the silver lining - clean title and a few odds and ends that could be reused like a gears, stage6 clutch and bell, cp21 carb and some other odds and ends.

Add to that, the bones were there with some of the hard to find parts like seat and wheels all sorted and ok, and did I mention clean title? It's wild how much just a clean titled frame can go for.

I had an Athena stroker crank brand new in box and a good set of forks from my other bike, so I met up with the guy and bought the thing. It was in a bit worse shape than it looked via that Facebook ad, but still a good base. Here are some pics from the original ad:














First thing I did when I got it home was cover those stickers with masking tape LOL. Didn't want my kids seeing it in the garage with those haha.

When I get more time, I'll update this thread with some more pictures of the build process and what went down. This thread will sort of be a catch-up to current day diary for now since as of today I have it running and back together but it is still a build in progress.

To sum up my feelings on this bike, I LOVE this bike and it might be my favorite one right now. It's so daily-streetable, wheelie-able and sips gas, all while being pretty darn quick and fun. More to come.

[aeroxbud]

Yes they always look better in the pictures. But it's great when you can save them. Even if your wife hates them.

[billwill]

Oct 22, 2024 6:48:49 GMT -5 aeroxbud said:

Yes they always look better in the pictures. But it's great when you can save them. Even if your wife hates them.

LOL indeed. I'm at #4 now and one definitely has to go. It will either be my Vento Triton, which I've had for 20 years now, kind of sentimental to me though, or the race prebug which never really gets ridden.

[aeroxbud]

Oct 23, 2024 5:02:19 GMT -5 billwill said:

Oct 22, 2024 6:48:49 GMT -5 aeroxbud said:

Yes they always look better in the pictures. But it's great when you can save them. Even if your wife hates them.

LOL indeed. I'm at #4 now and one definitely has to go. It will either be my Vento Triton, which I've had for 20 years now, kind of sentimental to me though, or the race prebug which never really gets ridden.

The wife has been saying for a long time one has to go. They are all still here.

[billwill]

Again, this sort of an odd thread for me, and going off of memory up to current day over the past year.

When I got the bike and started to tear it down and clean it up, I found oil everywhere. I don't know if this guy was just filling the oil reservoir in the dark after 13 beers or what, but this thing was FILTHY. I did the best I could to get where I could.

Next was taking the engine out and jug off. I don't know what was going on but I had a heck of time getting the cylinder off. I suspect with it being a malossi iron kit, the studs had rusted to it and I beat the thing to hell in the process. I probably spent too long trying to get the thing off without removing the studs, stupid me, but eventually I came to my senses.





I hemmed and hawed for a bit over wanting to do an Athena 80cc or not. I already had the crank, brand new in box, and knew if I didn't, I would regret not trying it. It's a rather permanent decision, since it involves cutting into the case to make room, so I got busy with the dremel. It's not pretty by any means, and certainly not as good or performant as milling would be, but I wanted to take pride in doing it myself and didn't feel like dropping $200-ish dollars into this thing. Some test fitting and pics of the crank finally in and clearing the case:












This felt pretty good.




At some point, I started to get into the transmission. It came with a good set of bits, including stage6 MK2 clutch, unknown blue contra and stage6 bell. I went ahead and ordered a multivar variator and added that.

Getting the clutch and rear pulley off was... a chore. It would not budge, so I had to use a freaking pitman arm puller from a front end service set to get the thing off. It worked incredibly well haha. 



I remember posting something on Facebook at the time about it and my solution and guys were berating me for the method, but I knew it was perfect. So I'm not sure how but it was like the primary shaft was the wrong size or too thick. I checked the clutch and pulley on other primaries I had lying around and the issue wasn't there with them.

Also, the previous owner said it had "gears" so I wasn't quite sure what was inside the gearbox. I checked final gearing and it ended up being a whopping 8.4:1 LOL! It sure did have gears and I'm not sure how this guy was getting along with that gearing on a malossi cast kit haha.

A while back I made a google sheet with prebug gearing specs (feel free to use it yourself) and based on some tinkering in there I figured it must have 14/42 primaries and 15/42 secondaries. I swapped back in 12/48 stocker primaries to put me back up to 11.2:1. 

Here is that sheet if anyone wants to use it: docs.google.com/spreadsheets/d/11pcGqDPZAR7nNoF6qcUUmcAwCDoOAvtzEuQm5Js0cVs/edit?usp=sharing

I finally got to a point of throwing the Athena cylinder on and this is the only pic I have of that. It comes with a (pretty thick) metal head gasket. It doesn't use an o-ring gasket. This proved to be quite the issue and even with the thinnest metal base gasket my squish was coming back at a whopping 1.4mm. 

Athena recommends a recommended squish of 1.2mm (I know, this seemed stupid high to me too) so I slapped it together at 1.4mm and sent it knowing I may have to come back and set it lower by shaving the head, cylinder or using copper spray in place of the gasket. 

Here's a video of the first start with a polini 4 race I had laying around. Sweet sweet two stroke ping.



After chatting with a buddy on Facebook who had a lot of experience with this kit, he recommended getting squish to .8-.85mm so I ended up removing the head gasket and using copper spray and crossing my fingers. It came out to .8mm on the dot and I was very happy, it held too with not leaks.

All I have time for, for now, will hopefully provide another post soon with updates that cover it from this point to current day. Cheers!

[billwill]

Got the bike up and road worthy enough with some cheap brixia body panels to start some testing. The gearing sure was high but I was still impressed with the torque for 8:1 final gearing. I was able to get around 60 on flat ground and slight downhill sections but getting there was doggish. 





Finally got around to swapping out the primary gears for something shorter and wound up with a final ratio of 11.2. So right now it has the following gearing:

12/48 primary, 15/42 secondary, for a final of 11.200

That did the trick! The thing has much better torque and acceleration and kept the top speed, if not making it climb a little higher than before with the taller gearing. Here is a recent pass using dragy. I'm honestly very surprised with the results. It may have had a little more in it but I'll take an 11 second 1/8th mile and top speed of 64mph for now!



The choke was never operable with thing either. The old cp21 card was able to be jetted correctly with pilot and main (36 and 96 is where I am now), but the choke, man oh man... I'm not sure what the guy was up to with thing but when I finally dug into the carb, I found what looked like dirt, sawdust and/or (I'm not joking) concrete??!, that the choke passage had been plugged with. No idea there, but decided to call it quits trying to salvage what was once a good carburetor and steal the identical cp21 off my Typhoon. Ended up ordering a cp23 for the Typhoon and this one will take the 21.

 


New carb with working choke was nice. Was able to start the thing with choke now rather than taking the air filter off and covering the intake with my hand when kickstarting and for the first 30 seconds or so. So that's nice, LOL. 

Next up will be some work on the front brakes. I REALLY need to do this as I've been putting it off and with my setup (older '99 forks and later '01 front wheel and disc) the caliper only grabs about half of what it should and the brakes are weak. I have a new larger disc. Upon looking more closely into the front brake situation I ran into something I haven't seen before: it seems like the front disc is riveted on?? So if anyone has any tips on what's going on here or how to remove it, I'm all ears.  

[aeroxbud]

That's strange about the disc bolts. The only thing I can suggest is heat to free the Loctite. Then either a punch to tap it round. Or a stud extractor.

[billwill]

Nov 2, 2024 12:47:23 GMT -5 aeroxbud said:

That's strange about the disc bolts. The only thing I can suggest is heat to free the Loctite. Then either a punch to tap it round. Or a stud extractor.

Ok so I figured it out - apparently they weren't rivets but magnets. Trailtech and other speedos offer magnets that fit a 6mm hex bolt and tuck right inside. I have no idea why this guy had plugged all of the holes as you should only need one for the speedo. In fact, I have a trailtech on my other bike and it came with one, but not one to fix a 6mm hex. It just sits somewhere on the rotor.

Getting these out had to be done with force. They were so stuck and corroded that I had to take a punch and use the pulverization method 

Got them out and the new rotor on and we are in business with MUCH better braking power now that the front caliper sits right and has full grab on the disc!














Only a few things left to do with this guy before good is good enough. Really want to go out and do another speed run with dragy now that I have a proper carburetor and have tuned some other bits but all I have a few more things left with this guy.

[aeroxbud]

That looks good. What size disc did you end up going with?
Looks like you have plenty of room to remove the caliper without removing the disc, which is nice.

[billwill]

Nov 3, 2024 12:16:22 GMT -5 aeroxbud said:

That looks good. What size disc did you end up going with?
Looks like you have plenty of room to remove the caliper without removing the disc, which is nice.

I’m pretty sure that it is a 200mm but it may be 180. It looks like it clears but no dice! Gonna be a pain to take apart and put back together but hoping I don’t need to do it again soon. Juggling the disc and caliper is an added nuisance but I’ll take it for the trade off in stopping power.

[aeroxbud]

That's always the problem with 10" wheels. But you definitely needed better brakes.