Problem with CT70H Flywheel

[Austin Ewald]

I have a CT70H with a mitusbusi flywheel on it, its giving me troubles. I think the flywheel magnets are not strong as they use to be, there for not giving good spark. I'm looking for a way to recharge this flywheel. But don't think thats my only issue with this flywheel that where the key sits. usally shears off and I have keep buying more keys. The groves on the wheel don't look like much left of it. Anyone who can help me out in any way I would thank you alot!

 

[allenp42]

I doubt it's your magnets in the flywheel. More than likely, it's your points, condenser, ohmic connection somewhere, or "all of the above".

Shearing off the keys is a separate problem. Would be helpful if you could take a few pics of the keyway in flywheel and crank shaft. Without this, it will be a guessing game.

 

[Austin Ewald]

Points and condesner been replaced by a electrical box type deal, my flywheel kinda still has magnetically still in it, just not as strong. And as far as the flywheel key, I had a am flywheel and stator from dratv, and everytime it fired, the key would sheer. But it could be that I need to buy a new key. Thanks for you help

 

[allenp42]

The inside of the flywheel appears to rubbing something. At ~ 6:30 position in the pic, and also to a lesser degree at ~ 5:30, I see some grooves where it looks like it is rubbing something? Could be that it's catching on something and that is shearing the key.

I really can't tell from this pic if the keyway in the flywheel is knackered or not. I'm assuming that you have one of the conversion kits from e-Bay that converts the points system to an electronic ignition? If so, I have no experience with this setup, but based on what I've read here, they are hit or miss on the H engines.

I'm sure that others will jump in here with better advice than what I can provide...if that's what you have.

 

[69ST]

The woodruff key only indexes the flywheel. It's the hex nut that holds it in place; when it fails to do so, the result is a sheared key.

Over-torquing the nut is NOT the answer. You may need to add a washer to get the flywheel pressed firmly enough on the crank taper. It's the interference fit that keeps the flywheel from rotating on the crank. As for you weak spark, doubtful that the cause is weakened flywheel magnets.

 

[Austin Ewald]

I will try a new key. As for that I also bought a new timing chain as everytime it did kick over. it jumped timing off so hope a new chain will fix that.

 

[69ST]

You're giving the impression that this engine is long overdue for some mechanical attention.

If you're replacing the timing chain, then the roller, idler & tensioner piston cap should be replaced too. Those are wear parts and the polymers from which they are made don't improve with age. Take a look at the cam & oil pump drive sprockets,as well, before ordering parts. Replace either, or both, if the teeth are worn. Worn oil pump drive sprocket teeth usually mean the oil pump has been binding.

 

[OLD CT]

Here's my .02 cents. The smallest amount of oil or most common too much points grease can F up your spark and one more thing, where the hell are the advancing weights!
The inside seems oily/greasy and minus the advancing weights.

AHH! re read! You purchased the cdi conversion? They DO NOT work on a 4 speed!
A lot of members here tried it and failed miserably... I got lucky and didn't try it!
Get the points and advancer back in there.

 

[Austin Ewald]

This bike has been converted over to electronic as I could never find any decently looking parts for the stator area

 

[OLD CT]

Is it the xrarespares conversion? It's NFG for a 4 speed. I have it on a 3 speed Hitachi and it works great. The Mitsu 4 speeds, no good.... Ask our very own Mike here.
Type in xrarespares in the search engine here for more info.

 

[allenp42]

I have a complete set of Mitsubishi coils if that’s what you need?

But I think this may only be part of your problem. Would suggest you fix what is causing it to jump time. I agree with racerx; sounds like you’re overdue for some engine work.

 

[Austin Ewald]

This summer I had replaced the head with a china clone from 2fast moto. My dad and my uncle put a new piston in it sometimes in late sevenites then since sat until spring this year. Which I had gotten it running. Then it went down hill when I put the new head on(still fired) didnt run when I hade this 20$ fly and stator from dratv. but fired once and while. then broke the welds on the cam lobes advancer. So I had to quit going that way. My plans are to up the cc on this, and if the 3 spd electronic ign works I could put a stroke and switch over to that.

 

[Austin Ewald]

I had contacted the seller of this cdi. told me to flip the ign coil then "should" work ok. Guess now is a waiting game on these parts. Hope I can get the engine going as I have plans to get this bike back on the streets

 

[kirrbby]

Was the aftermarket flywheel and stator setup from dratv made to use on a H (4 speed)?? That may have been at least part of the problem there. The crankshaft 's are different between 3 and 4 speed engines.
We have not heard of anyone making the xrarespares CDI conversions work with the Mitsubishi flywheels, only the Hitachi's.

So your original Mitsubishi stator parts, and timing advance mechanism are no good?? Broke? Missing? No longer a option to repair the original stator setup?

If you are looking to build the engine up big, and you're interested in converting to a 12v CDI setup, may be best to just cut to the chase. Buy a new crank and ignition setup from a reputable vendor. Then build your motor around the new crank.

 

[69ST]

If you are looking to build the engine up big, and you're interested in converting to a 12v CDI setup, may be best to just cut to the chase. Buy a new crank and ignition setup from a reputable vendor. Then build your motor around the new crank.

Had that same thought. Going to a 108-124cc bored & stroked motor is a substantial investment...too much to be based upon a questionable ignition setup. Back when this board was first created, the xrarespares CDI conversion was a good setup, a lot of bang for the bucks. Unfortunately, the earlier production run was sold out and this latest one has come with its share of horror stories. Yours follows the pattern. A fellow member here got the same instructions and they didn't work.

Going to 12v/CDI is a good idea. You'd be better off using a 12V Honda alternator and CRF50/70 parts are a dime a dozen. If you don't need lights, just source a used CRF alternator (flywheel & stator assembly). If you need lights, then either wind the lighting coils or, if that's not within your abilities, go to Ricky stator for one that's ready to use, with the OEM 12v Honda flywheel. Honda CDI modules & rectifiers are readily available and stone-reliable...just the ticket for a dependable street bike. From there, it's mainly just sourcing the 12v-style stroker crank, along with the piston to match the 12v compression height and combustion chamber (dome) of the head you're using.

 

[Austin Ewald]

so if i used a ign assemblie from a crf70, I would need the crf70 crank? or will a stroker crank work on it?

 

[kirrbby]

With the crankshaft you have, the CT70 H crank, you HAVE to use one of the 2 H stator/flywheel assemblies. But if you are planning a full rebuild of your engine, you can choose any crankshaft you want. So, in that case, decide what type of ignition system that you want to use, then pair it with the appropriate crankshaft. If you're building a street machine, and you want to keep up with traffic on a 45mph limit street, you'll probably want a stroker crankshaft. If you want to light up that street, and be seen, you'll probably want 12v lighting. So, buy a big bore kit with the 12v style stroker crank for 108, 117, or 124cc's of minibike power.

If all you want to do is get your bike running, you really need to buy a good used CT70H type stator and flywheel. They are pretty expensive tho. And a used part will likely be needing new points and condenser installed...at least points.

 

[Gary]

Some people think that the key holds the flywheel in place when in reality it merely locates the flywheel in the correct position. It is the taper that really holds it in place. If you suspect the taper not holding correctly you can leave out the key,put some valve grinding compound on the taper portion and lap the flywheel to the crank. Just make sure you clean it all off when you are done.

 

[Austin Ewald]

Well I got the parts for the timing, put it in. Timing was on point. Before timing was down a tooth, no matter what it would not get right on the mark. Chain isnt loose like it was before. Hope this helps a bit

 

[Austin Ewald]

@OLD CT I just got the bike back together. I did what the seller told me to do with the stators. put gas down the cylinder, carb off. Kick the bike over. It wants to run. I put the carb on. Hook up the fuel. kick it over and over. wont even want to run. take the carb off, more fuel down the cylinder. it wants to run. Its a cheap carb from ebay so would it be worth just buying another one or what does any recommend for a carb?