70cc kit worse performance than 50?

Set up:

78 pinto e50

15mm bing w/ 82 jet

Proma Gp Exhaust

70cc airsal kit w 70cc hi compression head

So i got the 70cc Airsal kit and 70cc hi compression head and installed it yesterday.

I followed the break in procedure here http://www.mopedarmy.com/forums/discuss/7/165899/165899/

Before installing the kit I was getting 31 top with the stock 50cc.

With the 70cc head and kit on I was getting 30 as my top speed.

I then bolted the stock 50cc head back on I was getting 35.

I didn't port or case match it , so I know im not getting the full power (thats my winter project).

Why would the high compression head perform worse? The top speed was lower and acceleration felt the same with it on.

I have no air leaks and have adjusted my point gap.

Also, on the performance sheet, others are getting 45 with the same set up but instead of a proma gp a techno estorill pipe. Does that pipe give 10+ mph boost?

What gives? What should I check next?

Re: 70cc kit worse performance than 50?

You did something wrong, period. You should be getting 40+ with that setup tuned mildly ok.

Re: 70cc kit worse performance than 50?

What's your gearinggggg

Re: 70cc kit worse performance than 50?

50cc head could have a smaller combustion chamber volume than a 70cc high comp. You have more compression.

If you think you did everything right, including jetting and timing, make sure it's not something dumb like your wheels are locking/rubbing on something. Good luck finding the problem.

Re: 70cc kit worse performance than 50?

what does your plug look like? 82 jet sounds a little small, but should be close..

what is your compression using a gauge?

Re: 70cc kit worse performance than 50?

yeah something is wrong, i get good compression and 40+ with a 14 bing and estoril and that kit with the 70cc hi-comp head, thin base n no head gasket. it's on a za50 stock gearing. how much gasket u got on there?

Re: 70cc kit worse performance than 50?

this was also before case match btw.

Re: 70cc kit worse performance than 50?

My gearing is stock. 16 x 45.

I dont have a compression gauge.

Plug pic is attatched. It looks a little darker in person.

Anyone in chicago want to make a few bucks this weekend that knows their shit and help me fix this?


Re: 70cc kit worse performance than 50?

Rob @t ATTN! Burrito /

umm you saved a three hour job for a winter project?

Re: 70cc kit worse performance than 50?

are you sure your timing was set properly?? cus that would probably do it...im running almost the same setup with a 12 bing and a 50 hi comp and im hitting 45 or w/e...but my point gap closed on me today and it rode like shit was barely hitting 35....opened up the points and zomgg...thats all it took...so recheck your points..

Re: 70cc kit worse performance than 50?

yea im with rob . why the hell would you want to tune this to an unmatched case then do it all over again after doing it right.

Humming a kit on an e50 with those tiny transfers isnt worth not doing the case match.

and your kits not broken in so why not just run the regular head till it its, its probably got too much compression. the compression ration goes all over the place during break in.

Re: 70cc kit worse performance than 50?

case matching, even done right, with an air die grinder, can be a half-hour job. not a winter project.

Re: 70cc kit worse performance than 50?

Man you guys are fast with the port match. I've spend hours/days with the files and sandpaper after I Dremel getting every little dimple and ridge out.

Re: 70cc kit worse performance than 50?

I'm actually running non-matched as of a couple weeks ago.

I found out my crank/bearings were wandering, and I wanted to go on a ride the next day. I quickly swapped out for another e50 I had lying around. I thought about matching it, but

a) I was lazy and didn't want to tear it apart

b) I don't keep silly putty around

c) I figured if I was trying to ride the next day, tearing apart a case would leave alot more room for error/not riding.

Still hit 45+ with an estoril, metrakit and del, but It didn't wind out to about 50 like it did before. Really annoying because I had been running that setup for so long and I felt like I hit a brick wall without it.

once you're used to it, 50+ = Weeeee! 45= meh

Re: 70cc kit worse performance than 50?

plugs a bit rich check your timing and points. they might have slipped one way or the other.

Re: 70cc kit worse performance than 50?

really think you need a smaller jet

Re: 70cc kit worse performance than 50?

talk to the dude with the red sachs G3, i hear he'll touch your bike with his hand and it will do wheelies like the love bug...

Re: 70cc kit worse performance than 50?

Besides rechecking your point gap and timing, you are most likely running too rich. If you still have the stock airfilter take it of. If it runs better without it, you are too rich on your jetting,means install a smaller jet.

If it runs worse you are too lean, install a bigger jet.

I run a 70cc piston ported Athena on my Maxi and hit 40+ no problem. 15mm aftermarket Bing with a 72 jet.

Bonne chance

Re: 70cc kit worse performance than 50?

Ugh, so I case matched it today (badly) and then when i was putting it together, I somehow fucking broke my intake manifold. High quality bing parts. So I put my 12 back on ( till a new one comes) and its still hitting 36. I did a plug chop and it actually looks like its running more rich, but its dying at stop signs. Obviously im not going to tune it with this on because well its only going to be on for a few days.

Anyways, As far as the point gap / timing goes, I set it to full advance and the gap to the size of the cardboard in a spark plug box. Besides this, what do I need to look for when setting it? Do i need to set the gap larger?

oh and I have the high flow air filter from treats.


Re: 70cc kit worse performance than 50?

dude , its running rich at wide open and starving for fuel at the stop lights.

raise your needle or wait till you can feed it properly with a real carb.

a 12mm carb wasnt designed to feed that kit. It was specifically designed to strangle a 2hp bike into being a 1.5 or a 1hp.

give it a rest till you get a real carb and intake your gonna soft sieze it.

Re: 70cc kit worse performance than 50?

Its a 15mm carb. It has a 12 intake on it currently, because im apparently the strongest man in the world and cracked the 15 mm intake. I just threw it on to ride around the block a few times after case matching. I'm not riding it till the new intake comes some time next week.

Re: 70cc kit worse performance than 50?

-Brian- The Ruffians STL /

It's too rich, your plug looks way too dark. Downjet a couple sizes and I bet it stops dying at stop signs. It's too rich. As you break in, you aren't even going to be able to start it anymore and you'll get stuck peddling home. It's too rich. Oh yeah, you'll go way faster too. hey, did I mention it's too rich, yet?

Re: 70cc kit worse performance than 50?

My Express did the same thing till I opened up the combustion chamber to the same size as the piston....Hauls ass now.....

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