'99 Prebug Zuma Build

[ryan_ott]

I ground that lip out so I could adjust height to my liking. Keep in mind if not torqued properly the legs could slide through the stem. A small angle bracket coming off of one of the clamping bolts could give you some reassurance. Others have left that ridge in place and cut the spring to adjust height. I had put many years of use with my method.

[billwill]

Feb 14, 2024 19:47:34 GMT -5 ryan_ott said:

I ground that lip out so I could adjust height to my liking. Keep in mind if not torqued properly the legs could slide through the stem. A small angle bracket coming off of one of the clamping bolts could give you some reassurance. Others have left that ridge in place and cut the spring to adjust height. I had put many years of use with my method.

Gotcha thanks man. I went ahead and did it. I’m going to throw some loctite on the bolts and mark the stanchions with sharpie so I can periodically check to see if they’ve moved, but, they are so hard to move even without prying the opening with a flathead screwdriver, that I’m not at all worried.

Stoked to get rid of the cali lean this thing had.

[Timmer]

I’m always happy when people start tuning their vehicles (be it cars, bikes, scooters, electric steps,…) when they don’t forget or ignore the brakes.
Going fast(er) is fun, but being albe to bring it to a controlled stop is important.

[aeroxbud]

Feb 15, 2024 13:57:27 GMT -5 Timmer said:

I’m always happy when people start tuning their vehicles (be it cars, bikes, scooters, electric steps,…) when they don’t forget or ignore the brakes.
Going fast(er) is fun, but being albe to bring it to a controlled stop is important.

Especially important in mopeds. Where the brakes are designed to be feeble and novice friendly.

[billwill]

Got the brakes all buttoned up and lowered the front forks by about 1.5". It handles much better and I can tell it has a fork/headset angle much more like stock now. 

The MXS race cylinder came last week too so I installed that and put the scootertube pipe back on. Moved to a B10HS plug and swapped in a 160 main jet to the PWK 24 just to be safe. MXS says anything from a 21mm to a 28mm carb is ok, but they recommend at 28mm.

I was considering removing the timing key just to be safe, but based on a few recommendations on the facebook groups, guys are saying keep it since I am running stock ignition. People seem to be able to get these tuned without a timing key or ignition at all but MXS recommends an ignition.

Threw the new jug and scootertube pipe on and waited a day or two for the hondabond to cure. It's crazy how low squish is for this setup at .55-.6mm. Just as wild is how almost identical this thing looks to the stage6 kit I was running before. Side by side, you'd think it was the same kit.

Works out for me since I did some mild transfer port matching for the stage6 and it matched up perfectly with the MXS. This was the only reason I didn't get the athena hyper.

Put it through 3-4 heat cycles (more than recommended but I wanted to get these in and re-torque the head bolts to be sure all of that was in good order). Also I swapped in some stage6 super hard clutch springs and a malossi red contra in anticipation of a higher engagement and belt grip needed. Thankfully this cylinder doesn't suffer from the same issues that the stage6 sport kit did with this pipe. Seems like a better combo. 

But, with all the idling and heat cycling, I think I may have actually fouled the cold B10HS plug. The bike acts like it wants to get into the powerband but begins to break up and sputter/lose power when power just starts to roll on. I pulled the plug and sure enough it was pretty dark (only on one side which I thought was strange).

I have a few more plugs on order, and I may just try running a 9-step plug that I have on hand to see if that fixes things. Temps never really got above 230 or 240º so I may just still be pig rich all around. I kept the carb needle in the in 2nd richest position like I had it on the other cylinder and from what I'm seeing these mxs cylinders don't love that and end up either in the middle or leaner with PWKs so I moved that up to the 2nd leanest position. It idled well with that change, something the stage6 never did. 

[billwill]

Thinking things may have been tuned too rich, I moved the needle up from the 2nd richest clip to the 2nd leanest.

Took it for a spin and temps shot up to 360º in pretty short order.

Wiping the plug down earlier and/or just switching to a leaner needle setting seemed to clear things up with the sputtering.

I’m thinking I need to move to the middle position or back to the richer one on the needle based on the temperatures I’m seeing.

Going to try that and see how it reacts.

[billwill]

Decided to leak test the setup and she was leaking like a sithe. Took me forever to figure out where too - there was a pinhole sized casting imperfection in the intake side of the cylinder.

I patched it with some JB weld and it held 6psi after that. Hopefully this clears things up and she runs well now. Who knows what jetting will be but I am guessing a bit leaner than where I'm at right now with a 160 main.




Haven't had time to take it out for a rip but it's idling better at least.

[Timmer]

I applaud you for finding that, I can’t even see it properly on the picture.
Have you contacted MXS about this?

[billwill]

Mar 5, 2024 8:37:08 GMT -5 Timmer said:

I applaud you for finding that, I can’t even see it properly on the picture.
Have you contacted MXS about this?

It was a royal pain... update since my last post: I went back and forth a bit with Scooter Attack. Their support tried to deny that there could be a hole or leak there and I pushed back with proof and pictures and they ended up refunding me the entire cost plus shipping LOL! 

Been insanely busy with work and life lately so haven't even had time to really ride but should be able to soon. 

[billwill]

Making some progress...

Finally got the time and break in weather to do some tuning. Now I just need to figure out what's going on with the Trail Fail Tech. Thinking battery needs replacing or a bad ground.

Running the 48 pilot and 150 main and needle clip in the middle seemed a bit rich. Ended up raising clip all the way to the top/leanest position and it runs much better now with temps not going above 310º or so, so I'm thinking it can be safely leaned up all around, or at least the main.

[billwill]

After many short bursts of tuning this thing over the past few weeks, I was able to take it out and get it running semi-decently!

Been battling the right combination of jetting and using the timing key or not. For a bit was not using it then swapped it in and was trying to get it to run not so hot but it would spike around 370-400º.

The problem was I was having to make it run pig rich on the main and needle to keep temps down but kept fouling plugs. Tried using the combination of the Tops variable CDI and timing key but that CDI would break down above ~10k rpm and begin to get sputtery at mid to full throttle.

Finally ended with running the timing key and malossi fixed curve CDI.

Jetting is at a 140 main, 48 pilot, JJK needle set to the middle.

I'm going to remove the timing key next and see how it goes because temps still shoot up to around 370 fairly quickly.

In the video, I didn't have a nice stretch of flat road so you can see how the bike shoots from stop to 45-ish then creeps up to low 60's. That was on a slight downhill to uphill but I think on flat ground I'd be breaking 70. Rollers are a mix that average to 4.6g or 28g total and it revs right out to 12,500-12,600 rpm. Right on the money for peak power for this kit. Might fiddle around and run 4.25s or 5.3s to see how it changes things after more flat ground testing.

[billwill]

Been tinkering with things the past few weeks and have some updates. I was chasing down an issue with hitting top speed and did a few things.

I ended up learning that the rear pulley wasn't opening all the way so installed a very small washer between the clutch and torque driver. I had to install another spacer between the clutch and bell so the clutch wouldn't hit the bell. The nut doesn't install all the way now so I consider this temporary until I can shave down some of the torque driver on a lathe or something.

I also found that the primary drive bearing was shot. So I just upgraded to the polini gear cover. Nice product.

Been battling carb tuning issues too and finally got the PWK24 dialed in but then got curious about swapping to a polini pwk30 I had laying around for another build. Swapped on the pwk30 and it definitely runs better on the top end and has more top end speed.

Big thing now is it pings or knocks at around 3/4 or 7/8's throttle to WOT. Thanks to 90GTVert for the example video you posted long ago that confirmed what I was experiencing. I have never heard or experienced this before but when I heard it I just KNEW something was off and it was a "not good sound" lol.

I'm thinking that I have a few options now to battle the knock and curious about what you guys think. In my mind I could:

- move to less aggressive squish
- stepping down to a colder plug
- running c12

None of these are ideal other than moving to a colder plug so I'm going to try that first. MXS recommends a b9hs plug with stock ignition and a b10hs with an aftermarket one. I have been running the 9 but have both on hand.

They also recommend squish be set at .55mm, which I felt at the time was so aggressive but I did it anyway. I think I've seen other setting it to .65mm. I really don't feel like going through taking the jug off and all the work involved with that so that leaves me with trying race gas or something with higher octane than pump 93.

Not something I'd want to be dailying but maybe fun to try but apparently c12 would be the ticket from what I read. Does anyone have experience running this or where to get it? Going to call a few motorcycle shops today. Apparently some guys will mix this with regular pump gas too. Maybe that would work for me as well.

BTW, new top speed on this is 66mph and I know she has more if I get this knocking figured out and can get a WOT rip.

[bigmatthew86]

Definitely run the colder plug. Also could raise the needle a notch to richen it up a little & see if that helps. I also wonder how much fuel is left in the line & filter when getting gas. We’re dealing with a gallon of gas so if there’s a quart or more of 87 sitting in there we aren’t really getting 93. I could be way off but it seems possible. Maybe go top of your car with some 93 & then fill up a gas can so you know you’re actually running 93.

[billwill]

Apr 13, 2024 11:22:24 GMT -5 bigmatthew86 said:

Definitely run the colder plug. Also could raise the needle a notch to richen it up a little & see if that helps. I also wonder how much fuel is left in the line & filter when getting gas. We’re dealing with a gallon of gas so if there’s a quart or more of 87 sitting in there we aren’t really getting 93. I could be way off but it seems possible. Maybe go top of your car with some 93 & then fill up a gas can so you know you’re actually running 93.

That’s actually a great point and something I’ve never even thought of but seems so plausible. Big petroleum is gipping us haha.

Hope the colder plug helps and that I get time to try it out today. I’m hesitant to move the needle any richer since this build loves to foul plugs when rich and I’m already in the middle clip position but it’s worth a try and I’ll keep that in mind.

[billwill]

Well, what I had feared was true. But at least I found what I believe to be the root cause of knocking. 

Measured squish and it was between .49 and .51mm. Yowza. 

Replacing gaskets and setting it higher this time. Really don’t know what happened. Maybe when I retorqued the head after a few heat cycles things settled a bit.