1988 DAX for sale in Mi.

Racerx I never doubt you. Of course I did have to try spinning the speedo back and forth a couple times, hoping it would turn up 1000 miles. Nope. Sticks right back in the same spot each time. Open heart surgery it is. I'll either revive it, or make sure it's good and dead. One or the other. It's on my list for the off season.

Snow!!! No!!!!!

I thought it was spring time?

Welcome to springtime in beautiful Davison Michigan.

That snow has already disappeared but they ARE calling for accumulating snow :-/

We had the same last night ,already melted as well .Just a little above freezing today and for the next few days .

Well, you know how things go in "The Great Pothole State"...at a glacial pace. This is April Fool's day weather, "emergency manager" style.:19:

Well my odometer jammed up when it tried to roll 1000 miles. I opened it up to investigate. Turns out the...odo dial itself...the numbered wheels I spose, seemed to be the problem. When it jammed, it chewed a couple teeth off of a tiny brass gear that was permanently mounted. This speedo is from a CT90 and the CT70's don't have the same brass gear. So I bought a donor CT90 speedo off eBay to rob the gear. The donor turned out to have the threads that the cable screw to busted off, which meant I had to actually remove that tiny gear on both parts and put the good gear onto my original.
Long story short....CT70 K0 speedos are tricky to work on. CT90 speedos are a much bigger PITA. But, I think I got it repaired and ready to go back on the bike. Back to zero miles.

Agreed, I've not restored many of the NIPPONDENSO units but they are a mutha. I'd have wanted to know why the odo stack locked-up in the first place. Sounds like someone may have been inside before and gotten the little indexing gears wrong...between the digit wheels.

Ahaa! That was what I had decided too. I know for sure it was into since I bought it from the guy who was in there. He touched up paint and reset the odo. When I took each wheel off I could see it was possible to put them back wrong, but I wasn't paying attention to whether or not it WAS wrong. Anyway, I ended up using the dial from my donor speedo when I put it back together. That one had not been tampered with, including by me. It had 11000 miles on it but was nice and clean. The numbers looked about the same as the old one as far as being dingy dirty, so I swapped in the complete dial. I think I put the old one back together correctly, but just decided not to use it. In the end. Also used the glass with gasket from the donor as it looked better too. Couldn't seem to get the old glass clean around the perimeter. The donor also came with 4 nice lighting pigtails if I ever want to use them instead of my homemade ones.

Had a liitle warm weather here today, so I stole some time to play with my minibike. Pulled it out into the light and put my repaired speedo back in. Put 3 new led bulbs in, using the sockets and pigtails that came with the speedo that I bought for parts... The correct wires for this CT90 speedo.

New bulb to fix the burned out taillight. Added air to the tires and a little gas in the tank. 2 slow kicks then it fired up on the 3rd. Warmed it up and went for a short ride. First of the season.

My speedo and odometer are working great. Odo shows 9 miles now, but I think the motor actually has about 1400 on it. Man, felt good to go for ride. Lookin forward to riding it to work, soon I hope.

Next thing I need to do to this bike is hang the oil cooler... then mount the petcock to get reserve back...then come up with a better footpeg/kickstand setup.

Well is seems that a xr70 type kickshaft and pinion gear are NOT right for a trx90 transmission.
I think I put about 3k miles on this motor, then my son added some miles, before the kicker started chunkin.
The kicker always felt kinda fragile...guess it was.
Broke my heart to tear this motor apart...sucker ran like a champeeen! Further broke my heart to see that it was put together with spare parts and bubblegum. But again...sucker would RUN.

Anywayze...here I is.
Need a new cylinder, and a piston kit to match the Modernworks 4v head. Some light scoring on the piston, and the cylinder...it needs to be replaced.
Need 1st gears...will just replace both trans shafts complete.
Need a correct kick shaft, complete.
Need a good cleaning...cam chain probably...etc.

Think the crank, head, and clutch's are good...but I'll be checking them out...crank is still a ?

Ouch!

There are a few lessons to be learned here.

First, I reckon, is verify tooth count of every gear.

Second, the kickstarter setup is inherently weak...because only half the gear width engages. The common fix is using a 12v - style constant-mesh kickstart gear & shaft assembly, if your tranny is compatible. Kickstarting technique still matters. I see too many riders who slap-kick the bejeezis outta these things then wonder why they fail.

Have to wonder who would install a fire-breathing top end assembly then half-ass the bottom end...that has to withstand the increased mechanical stresses?

You're giving the impression that this motor was a grenade waiting for someone to pull its pin.

3000 miles ain’t much of a life. A China engine will usually last longer. Proper kicker and a much easier break in. Sounds like it overheated. A cooler seems to be a must.

OLD CT said:

Sounds like it overheated.

Click to expand...

Why do you say that??

I almost agree. I think a cooler is a ...really really should. But I don't think it's a must.
I didn't see any sign of overheating as I took this motor apart.
The ONLY real problem that I found was that the wrong kicker was installed. No question, it was wrong. It was a grenade as Bob mentioned...just a matter of time before it started eating 1st gear. Kinda surprising that it DID last as long as it has.


I actually rode it around the block before I drained the oil and dropped the engine. (I know...but I like to live on the edge.) It was still running great...1st gear still ran smooth, as well as 2nd 3rd and 4th.
To be honest, if I knew this motor would only last 3000 miles between complete rebuilds, I think I'd still rebuild it, over and over.
I don't have a bad word to say about the build, but I'm A LITTLE peaved about HOW it was built.

3000 miles isn't much. The better Chinese lumps such as 110-140 Lifans are 6000-milers. The S-cut Takegawa setups (skirtless piston) lasted 4000...and those only needed to be "ring slapped" (new piston + rings) owing to their Nicasil cylinder linings.

Peak oil temps are a bit more involved than some realize. Some tunes are capable of making 16hp+. The z50 engine originally made less than 3. That's a lot more heat and it's dissipation/flow pattern is not completely known...hence we want to stay on the conservative side with oil temps...as we are able to monitor them.

As for the weak kickstarter assembly..
there are fixes.

it should last longer than 3k for sure. I've used the CHP kickstart shafts and they mesh perfectly. I don't know what piston matches that modernworks head, but I'd bet it is the +r head for takegawa or the V2 head from TB matching piston. They make em in 52 and 54mm.

Scored piston and cylinder that the cylinder is beyond ''a new piston/ring slap'' at 3k is what made me think, it ran hot. Cooler, cooler, cooler... Trying to give you good advice.
You will enjoy more time riding, not wrenching.

It never ran hot. Highest temp that I ever logged on this motor was 105C. During break in was the only time I had to limit my speeds because of temps. That's 124cc's with no oil cooler. No sign of overheating in the head, rod, cylinder or pin. It didn't overheat. The score marks in the cylinder I assume were made by the shrapnel from the gears shredding...see the pic in #191. That is about 60% of the metal and shavings that I found inside of the engine. I could probably hone out the cylinder...it's not bad at all. But the cylinder seems to have been modified...it's 67.5mm tall.?? And had a thick aluminum spacer under it...between 2 gaskets...funnybuisness... It's not worth saving. I'll have to pull these parts out and get some pics to post.

I am not arguing the fact that this engine should last longer than 3000 miles...lol. I must not be making myself very clear there. The reason...the ONLY reason this engine failed....only reason, as best as I can tell....is because the WRONG kickshaft was installed from the start. Obviously wrong.
The CORRECT kickshafts are available...easy enough to find. Had the correct part been installed, this motor would still be running and riding and kicking, and with NO oil cooler needed. Yes, NO oil cooler.
No cooler, no cooler, no cooler...lol

I have a piston kit ordered. Right from Modernworks. It's going to take a while to get...2-3 weeks is my guess.
It's a 4 valve piston. The original isn't hurt too bad, but I just think it needs to be replaced to do a good, and right, job. I'm rebuilding someone else's engine here...my son's engine. I want to make it right. So I'm buying the piston and rings that I know match the head. I'll get a cylinder from tb, and a kickshaft from DrATV.

http://modernworks-ltd.com/order/in...ct_info&cPath=103&products_id=247&language=en

Sounds good. No discoloring on the piston pin right? It must have been the metal circulating. It is jetted a tad rich if anything. Which helped keep it cooler. You are going to break it all down '' split the cases'' and clean all the metal out right?