70cc airsal cylinder kit wont work. (puch maxi k)

I've recently bought a 70cc Airsal kit. mounted it with no trouble but whatever i do it won't start at all... it ran perfectly before i mounted the cylinder and when i but the standard 50cc back on it runs fine. the moped has good igniton and lets enough fuel into the cylinder.

Im running 15mm bing carburator and a 28mm exhaust.

and a Racing crankshaft in the motor.

Ive replaced all the gaskets in the motorblock. ive tried with "motorstart" spray and fiddling with the ignition timing and different jet sized alongside with powerfiler and standard filter. but without luck.

i hope some of you "mopedheads" are able to help me. ;)

Re: 70cc airsal cylinder kit wont work. (puch maxi k)

Drake Abrahamsson /

Few questions that might not determine why it’s not starting but important nonetheless:

1) Did you get a new head as well? It should match the diameter of the cylinder.

2) Did you set your ring gap?

3) Are you using a needle bearing on piston/con rod?

4) Did you reuse your wrist pins on the piston? (never do this)

5) Did you properly torque your head bolts to 7ftlbs? (standard for Puch)

6) Did you buy a temperature gauge?

7) Did you rub a lil 2stroke oil on the piston/walls when installing as not to scratch either surface?

According to Freds Guide the 3 things you need to start a moped are spark, compression, and fuel. The thing you’re most likely changing is compression, but as we all know, it’s a lot more complicated than that.

What do you mean your moped won’t start?

Do the pedals lock up?

Can you spin the flywheel freely?

Have you checked for spark with the kit installed?

Forgive me if these are basic and redundant questions/advice, but from your posting it sounds like you’re trying to plug-n-play without much heed for any of the many intricacies of kitting a bike.

Post pictures (of the bike, cylinder, head, flywheel, etc.), those tend to help a lot and may even help somebody trying to help you discover something else entirely wrong with your bike. Hope this helps!

Re: 70cc airsal cylinder kit wont work. (puch maxi k)

Hello drakeabra, Thanks for you reply :)

1) it was a cylinder kit completed with the following, cylinder, cylinder head, piston, piston pin, piston ring, studs and gaskets.

2) i didnt set any ring gap.

3) Yes, i am using a needle bearing.

4) I used the pin included in the kit.

5) What do you mean?

6) i havent got one. what is it good for?

7) yes i did ;)

I Tested for spark after i installed the new kit, and even redid the timing.

i did test for compression after installing the kit, and i seemed to have great compression.

it wont idle og turn on with the new kit installed. The sparkplug does get wet.

i will have a look at it later today with a friend, ill make sure to get some fotos and will most likely be posting them today. (edited)

Re: 70cc airsal cylinder kit wont work. (puch maxi k)

♣Slew Foot♣ /

The cylinder base gasket has a different thickness and the new cylinder has a different port map. Your timing is winky hard to start= too advanced...

Re: 70cc airsal cylinder kit wont work. (puch maxi k)

#5 he's asking if you used a torque wrench to tighten the for nuts to the proper spec..meaning a wrench with a meter/clicker on it.

#2 The Piston rings aren't gapped from the factory. Once the engine warms up they can expand, the ends will touch and the bulging will catch on a port window. If that were happening, you would hear it but it prolly hasn't run enough...still a good idea to go in with a feeler gauge and check it in the near future.( I didnt do it on my first kit and never had a problem for 500mi. Same with my kstar. But I did kill a brand new Moby top end..thats when I found out about gapping :p)

How did you jet the carb? What emulsion tube are you running? Needle position?

Id bet either you diddnt set up the carb or you gotta leakypoo somewhere

Re: 70cc airsal cylinder kit wont work. (puch maxi k)

Drake Abrahamsson /

Setting your ring gap is pretty dang crucial. Use the table under the Ring Gap wiki here:(https://www.mopedarmy.com/wiki/Ring_gap)

& when I mentioned wrist pin clips I meant these bad boys (https://www.treatland.tv/12mm-malossi-wrist-pin-clips-p/malossi-wrist-pin-clips-12mm.htm). Some people say to NEVER reuse them even if only in for a little bit but you can test your luck- just inspect them to make sure they’re not too compressed or warped. There’s some good threads that tell you which kinds are best/proper installation to avoid over compressing them and therefore decreasing the tension holding them in place. One thing for sure is to MAKE SURE the protruding piece of metal is PARALLEL with piston movement (exactly directly towards or away from the head). If they’re not they risk getting compressed during high RPMs and ejecting, going on a destructive rampage inside your cylinder, ruining your new kit.

A temperature gauge (https://www.treatland.tv/trail-tech-digital-TEMPerature-gauge-in-BLACK-p/trail-tech-742-et3.htm , for example) let’s you know that you’re going to seize, before you seize. Anything above 400F is considered the danger zone and if you have this it'll give you enough time to stop running your bike, let it cool down, and avoid engine destruction. A lot of people consider them mandatory when running a kit. This is especially true if you’re new to kits and are experimenting with jetting.

Re: 70cc airsal cylinder kit wont work. (puch maxi k)

It’s that bing they no good

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