Pull start CT90 and other performance enhancements

So it's time to tackle this little Zombie chaser 78 CT90 I got for free and make it run again. At first I just wanted to basically do a resto of sorts and hang it up on the front of the motorhome to use as a runabout to explore trails or to run to the store when packing up would be a PITA. But the more I thought about it, the more I want to do something different, and more importantly, fix some of the shortcomings of the original design.

As reliable as these scoots are, there are things that can be improved and I'm aiming to do it it one fell swoop.

Cons:
-points ignition
-6 volt electrical
-limited power for a 200+ lbs person in high range

I have been researching some options and I think I have finally settled on a solution. That solution comes in the form of a Honda ATC 125M motor. It is one of the biggest factory Honda horizontal motors made and it has a fix for all of the shortcomings plus a few bonuses.

Pros of the 125M motor:
-CDI ignition
-12 volt electrical
-more power than the 90cc motor
-electric start
-retains the dual-range transmission
-pull start backup

I suppose one could just swap in a Chinese clone engine of up to 172cc (biggest that I know of) and get most of those pros but I think the dual-range transmission is part of the appeal of these bikes and is something I really would like to keep for both practical and nostalgic reasons.

I'm wondering if anybody has heard of this swap before and if they have any information on it. I have come across a few guys on the CT90 Yahoo group who have done it so I know it's doable but information is lacking. If I can't find more info then I guess I'll just learn it as I go and share that knowledge.

Also, any performance discussion for these horizontal motors is welcome.




Sean

Some pics of the neglected beast.



High-flow exhaust...


Top secret performance wiring mod...







Sean

wow, what a beast... didn't know you could swap a 125 ad have the dual range.. did honda make some dual range 3 wheeler that I don't know about??

I agree with you 100 percent about the short comings of the ct 90. I can't tell for sure but it seems even the 110's had 6 volt electrics, at a time when the c70 all went 12 volt (re: 82 passport)

Now, I can't believe you got it free, that is my favorite price. Oh, and I hate you... I totally hate you!! ..... j/k

I especially like that special rear wheel designed for riding on rails.

I don't have any technical support to offer here, but that seems like an awesome idea.

There were many Honda 3 wheelers with dual-range transmissions and the 125M was one of them.



It was free but it was my uncle who gave it to me so I'm sure he'll collect a few favors for it.



Sean

wow,.... i want an awesome 3 wheeler too. i bet lifan would clean up if they made that engine.

When your uncle calls, act sleepy and cough a lot!!

Is the 125M still being produced by Honda?

Not as far as I know. Nothing being sold in North America comes with this motor but that doesn't mean Honda doesn't make it for some other market.

Luckily these trikes are plentiful and easy to locate. I have already located a running motor as well as a complete running ATC in my neck of the woods.



Sean

suggest you join the ct90 ct110 yahoo group they can probably tell you how to do it. sure someone in that group of 3400 members has done it

Thanks. I've been a member there for the past year. I did get the idea from a few other members there but there hasn't been much info posted.

I also ran it by Jack at dratv.com and hope he can help me with the misc parts I might need.



Sean

Scored a (mostly) complete ATC 125M for the swap. The machine was rough and in a few pieces but the motor looks to be in running condition. As luck would have it though, it's missing the pull start.



Sean

I always wondered why a small motorcycle has a kick starter and a big ATV has a pull starter? I had to pull start my 500cc ATV once and it just about pulled my arm out of the socket when it kicked back.

Bummer. The motor I found is a dud. Looks fine at first glance, missing the recoil start though.
And the exhaust port is cracked which is common because they get hammered eventually.
But why doesn't the range selector do anything and what's all this goop for?



Let's have a look.



This is a primo goop job...
Too bad you can't really fix broken cases with bubble gum.

This gear has had some excitement...



Oh well, paid less than a C note for it and it came with the full wiring harness and electrics. Just that was worth the price. Probably get my money back from putting some stuff on fleabay.
The search for a pull start motor continues.



Sean

Gonk, where are you located... phoenix??

Northern Ontario, Canada. Little place called Valley East.


Sean

You probably already know about Dr ATV for parts.

http://www.dratv.com/engineparts3.html

oh darn, I'm in phoenix... the "valley of the sun" and I found this..

http://mohave.craigslist.org/mcy/1704117658.html I think this is the bike your talking about.

have you ever used "searchtempest" it's perfect for searching around large areas on craigslist.

Yeah I used it a couple times but Craigslist isn't as popular in Canada. We have Kijiji instead. www.kijiji.ca



Sean

Found two ATC 125Ms for cheap, going to pick them up on the weekend.

In the meantime, I decided to take the CT apart and at least see how well the 125cc ATC motor fits.




Pretty good. The mounts line up perfect as well as the sprockets and chain. The recoil case is a few inches thicker than the stock 90cc motor so I'm going to have to use the footpegs from the ATC which is also wider. That just means I'll be able to drag the pegs on the go-kart track!

I've also started taking the chassis apart to assess its condition and decide what to do about paint.



Overall it's very solid. The battery box area is the worst, presumably from battery acid spillage.
And also the swingarm bridge may be a bit soft too.




I'm debating if I should try and get it powdercoated or just paint it. Either way it needs to be sandblasted to get all the rust off and some new metal to beef up around the battery box. I'd also like to make it a different color than the factory yellow. Any suggestions?





Sean