Rocket Keys??

moosinatrix · Aug 25, 2012

Hey guys, its been a longtime since i have been here, but i had a quesiton for you performance nuts.

Rocket keys.... ever heard of em??? very popular in the pocketbikes. this product is a replacement for the stock crankshaft ket that holds the magnet part of the magneto in place.

What the rocket key does is offsets the magnet, and advances it to precisely 10 degrees.

My question is would this part fit a 66cc engine, they make 2 different rocket keys, one is not very long but average shape

heres a link to the part, it has pics with dimesions

http://motorparts4less.com/products.php?id=1118and size, that other seems to be elongated.

2door · Aug 25, 2012

Ten degrees advance is a lot. I've tried two and three degrees with good results but I wouldn't go 10. Just my opinion based on experimentation. You'll kill your low end power and possibly cause pre-ignition that can damage things. Be careful.

Tom

Huffydavidson · Aug 25, 2012

I have tried advancing the time someone wrote here and it lost power and run hotter. if you want to alter the timing on China girl get a Jaguar CDI from JNMOTORS.COM. or make 1 yourself .

ivan H · Aug 27, 2012

Yes, 10 degrees advance is a lot, especially if using the stock CDI that doesnt retard at higher RPM, & while advancing timing CAN make good power in some areas, it will generate more heat. People have filed the woodruff key to achieve this. I run 2 or 3 dregrees advance but the motor is far from stock & I use a home made Jag type CDI that has a little added capacitance in the retard network to steepen the retard curve even more. Cheers

biknut · Aug 27, 2012

I have a Manic Mechanic, adjustable magneto rotor I bought from BikeBerry.

Easy Rider · Aug 27, 2012

I tried one of mine from my go ped days in my Morini and it totally ran like crap so I 86ed it.

moosinatrix · Aug 31, 2012

thanks for the info guys, can anyone provide me more info on this jaguar cdi or how i build it out and install???

Also my current problem is i have a brand new motor that i bought, ran maybe half a tank through it and then it sat cuz the electronics went bad.

I got a new magneto (that is produceing current, it bit me pretty good)

and a 50-110cc dirtbike ignition coil that tested on 12v battery and known working.

but these parts dont work together. I cant get fire!!!!
Ideas???

ivan H · Aug 31, 2012

Hi, if u wanna build 1 of the Jag type CDI's, check the thread "Modified CDI & CR80 Coil" in High Performce Tips section or "Roll Your Own CDI" in Lighting & Electrical" where there's schematics etc for othertype CDI's as well. Cheers

Venice Motor Bikes · Sep 1, 2012

One thing to remember about air cooled engines is that you need to have the timing retarded to keep the engine running cool!

ivan H · Sep 1, 2012

Yes, this is right. I have been running a few degrees advance but since porting the piston in conjunction with reeds, & with the weather warming up, just the last couple of days I've noticed signs of detonation down low & had 2 retard it a little. I'll also keep an eye on mixture during our hot summer & run it a fraction rich 2 help keep it cooller. Cheers

2door · Sep 1, 2012

moosinatrix said:
thanks for the info guys, can anyone provide me more info on this jaguar cdi or how i build it out and install???

Also my current problem is i have a brand new motor that i bought, ran maybe half a tank through it and then it sat cuz the electronics went bad.

I got a new magneto (that is produceing current, it bit me pretty good)

and a 50-110cc dirtbike ignition coil that tested on 12v battery and known working.

but these parts dont work together. I cant get fire!!!!
Ideas???

I explained that to you on the chat board. You can not use a motorcycle ignition coil with the magneto in a Chinese 2 stroke engine. They are different breeds and not compatible. What you have is called an induction coil. What the engine is designed to use is a CDI, or capacitive discharge ignition. They aren't the same.

The CDI that came with your engine, the one you broke, needs about 80 volt AC which the magneto provides. Your motorcycle coil wants 12 volt DC.
As I told you, order a new CDI and enjoy your bike. The factory CDI will provide you with many miles of riding. The majority of members here who run the Chinese 2 stroke engines use them and have no problems.
Mount the CDI with a piece of double sided tape under it and don't over tighten the screws.

Tom

moosinatrix · Sep 1, 2012

well i have been looking into the jaguar ignition system, from what i have seen its a dramatic improvement. i just ish theere was a video of it in action next to a stock bike

Theon · Mar 1, 2014

I guess this is as good a place to put this as anywhere.
I noticed this a while ago and was going to start a new thread but this one seems appropriate.
I have 5 Ht motors in all, one is just parts, and there are three good motors on my bench at once, but in having 4 apart at once at the moment I noticed of my 4 Mag rotors 2 had decidedly more advance built in to the rotor key slot.
Im now curious to check my other motor, which does seem to ping a little at 8500 RPM.
If you look carfully at the photo you will notice the key slots are a different width.

Theon · Mar 1, 2014

I pulled the mag rotor from the Phantom out of curiosity, and used my $2 timing protractor to have a closer look at all 5 of my rotors and found that there were 3 distinctly different timed rotors with approximately 12 deg difference between the pair with least advance and the one with most. the other two falling roughly in between. And the one I just removed from the Phantom had the most. Which would explain it's pinging.
I found of the four cranks on the bench the keyways were all fairly close as were the width of the keyway slots.
The two rotors with less advance had very nice tight fitting keyways, the other 3 were sloppy.
So another case of not all Ht's are created equal.

2door · Mar 1, 2014

I have also seen rotors with different degrees of timing advance/retard. Several years ago I was trying to find out why two identical engines ran so differently and started comparing every aspect of those two HTs. The only difference I found was the keyway in the mag rotor. The better running engine, the one with more low and high end touque was about 3 degrees advanced over the engine/rotor that was retarded.

The strange thing was that when I swapped the two magnets the power increase didn't follow the rotor. There was a 'slight' increase in power from the engine that had been the dog but not as noticable as when that rotor was in the other engine. The better running engine with the retarded rotor suffered some power loss but it still ran better than the other one.
Never did find anything else different betwen those two engines. Same carburetor, same CDI, compresion was within a few pounds of each other. Same fuel, same bike, sparkplug, gearing and tires, everything. One engine simply ran stronger than the other one. The better engine was also quieter in terms of intake noise. And yes, I compared port timing, shape and size too. Go figure.

Tom

Wild Bill · Mar 1, 2014

If you measure the port heights they are all over the map too.

Theon · Mar 1, 2014

I've found at least 4 very different Jugs.
Always got to check port timing if you want to get the most out of a HT.
Also overall height of Jug varies all over the place.
They like to make it hard for the amateur.

maniac57 · Mar 1, 2014

I still wish someone in the aftermarket would cast a decent cylinder with good porting and a iron sleeve using modern materials and vacuum molding tech like the better engine brands.

I figure it is simply too expensive or Fred and/or Arrow would already have one.
I refuse to believe there is no moped cylinder that could be made to fit. I've never been a moped fan, but they have some excellent engines and I want a PUCH or Tomos cylinder swap kit.
NOW!

rogergendron1 · Apr 17, 2014

maniac57 said:
I still wish someone in the aftermarket would cast a decent cylinder with good porting and a iron sleeve using modern materials and vacuum molding tech like the better engine brands.

I figure it is simply too expensive or Fred and/or Arrow would already have one.
I refuse to believe there is no moped cylinder that could be made to fit. I've never been a moped fan, but they have some excellent engines and I want a PUCH or Tomos cylinder swap kit.
NOW!

i thought about drafting one up on auto cad and having my dad program a tool path on master cam to m ill one from a solid block of aluminum .... but that would be a one of a kind thing and we only have one block big enough to do it ands the time involved to make a solid billit block aluminum cylinder for a china girl would be too mutch for me i mean i would have to compleatly redesign the port shape and tranfer port shape and the tranfer port flow patern and figure out the max rpm the crank can handle and port map it somewhere in between to leave room for custom prorting, i believe i saw that there was enough room to bore it out and cast iron sleeve it larger tan 70 cc ...

i mean if your going to make your own jug why not make it taller and use a longer compatable rod and sleeve it the largest posable size ? you could probably get close to 100cc with a loger rod taller jug and a real oversized honda or puch piston....
and then one would want to machine a reed valve and third transfer right into the jug and make it a 100cc reed valve conversion right ??? iron sleeve and properly port mapped for the intake and exhaust and even tranfers for amx all around power but still leave enough room for pro to grind and customize

rogergendron1 · Apr 17, 2014

you can make a 7mm spacer and bolt on a puch jug and head and piston ...but i think the case needs to be bored some for the skirt of the jug to fit and the jug needs to be bored for 8mm studs also the puch piston will need to be cut down at the skirt for crank clearance but i know it works and works well it has been done by a member here before

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