Exasperated by puch maxi - runs good 1/4 throttle, dies above 3/4

Sam Moss /

Jun 15, 2011 04:58PM

Hey guys,

So a guy a friend who was staying with me for a while left his dead puch maxi behind, and since winter I've been tinkering with it here and there trying to get it running. Motor was seized solid before but I got that loosened up and here's what I've done since.

New (china clone) bing 15mm carb

Running on 60 jet (as per treatland's guesstimation/suggestion. Also ran it on 82 jet that came with carb, didn't run that differently surprisingly.

disassembled and cleaned piston/cyl/rings etc and all new gaskets

Took apart muffler and cleaned/derestricted, reassembled (baffle still there).

Symptoms: Starts and runs fine, but full throttle immediately causes motor to die. Sweet spot seems to be about 1/4 throttle, it can get my 200 lb ass up to 25ish on my short street. 3/4 throttle on is no good.

I'm hoping my jetting is the problem. I've tried all pin positions and shortest pin seems best. Does anyone have any suggestions? Eventually I wanna do a 70cc kit and pipe but I kind of wanted to get it running properly and make sure I can register it without any problems before I dump any more cash than I have to.

If it sounds like a clear-cut jet problem let me know what you think is a good guess and I'll buy a few in that range.

Thanks fellas

-sam

Re: Exasperated by puch maxi - runs good 1/4 throttle, dies above 3/4

Dwayne Hoster /

mightyducksrule

Jun 15, 2011 05:09PM

UPJET DUMMY 60 IS TOO SMALL OBVS

Re: Exasperated by puch maxi - runs good 1/4 throttle, dies above 3/4

Groove Champion /

bergw

Jun 16, 2011 12:30AM

what's the plug look like?

check the float too.

Re: Exasperated by puch maxi - runs good 1/4 throttle, dies above 3/4

[[ Linda ]] /

mycider

Jun 16, 2011 09:29AM

Have you checked for air leaks? It's surprising to me that it ran about as well with the 82 as it did with the 60.

60 is within the realm of reasonable jet sizes for a stock Puch, though. I've seen as low as 52 and as high as 72 in a stock Puch, so you're right about in the middle there. It might not run perfectly, but you shouldn't be THAT far off.

What about timing? Have you verified that that's correct?

Re: Exasperated by puch maxi - runs good 1/4 throttle, dies above 3/4

Sam Moss /

mossman OP

Jun 16, 2011 09:46AM

Upjet dummy was actually great advice. I threw the 82 back in (that the carb came with, that everyone said was too big, and barely ran when I first tried it) and it ran pretty good at all throttle positions. Might be some fine tuning to be done still, but way way better.

I have futzed with it a lot since then, changed the pin position, added racing style air filter I forgot to mention, cleaned points and reset timing, so maybe one of those things was the problem before, then the too small of jet became a problem. I'll buy some jets in the 70's regardless and tinker with it, but at least it's rideable now so I can shake down other issues.

Thanks for all the responses guys, especially Dwayne's instantaneous and straight to the point one ;)

Re: Exasperated by puch maxi - runs good 1/4 throttle, dies above 3/4

Michael M /

greenmikey

Jun 16, 2011 02:47PM

I really think that if you are jetted that high with stock everything then you almost certainly have an air leak. I guess I could be wrong but that sounds crazy high for stock everything + highflow filter.

Re: Exasperated by puch maxi - runs good 1/4 throttle, dies above 3/4

Don Sumpter (OFMC) /

Go to branch

donsumter

Jun 16, 2011 06:42PM

I think you have some crap in the gas tank that is letting just enuff gas to get into the carbto start it and get up to 1/4 speed but gets starved off for gas when you try to go faster>the same with a gas filter! check these and see.

Re: Exasperated by puch maxi - runs good 1/4 throttle, dies above 3/4

Sam Moss /

mossman OP

Jun 17, 2011 12:46AM

Need a brake cable now so until that comes in the mail I can't shake it down any further. Gonna do brake shoes and tires and get a few jets in the 70's as well.

Looking at the 82 and the 60 jet, the hole was much bigger in the 82. Obviously it should be bigger and I don't have a means of measuring that small to quantify exactly, but it was noticeably bigger compared to the 60, maybe twice the diameter, which is 4 times the volume. So maybe my 60 jet was bad or had corrosion or something and needed to be poked clear, adding to my problems. Gas tank was clear of rust and this is the 2nd or 3rd tank of gas I've had in it, filter is new and I haven't seen any particulates in the gas. Excited to have this thing on the road for next weekend...woo!

Thanks for all the help guys

Re: Exasperated by puch maxi - runs good 1/4 throttle, dies above 3/4

Dwayne Hoster /

mightyducksrule

Jun 17, 2011 01:03AM

GLAD YOU TOOK MY POINTER BRO!! WOOHHOO!!

Re: Exasperated by puch maxi - runs good 1/4 throttle, dies above 3/4

Sneaky Pure /

sneakypure

Jun 17, 2011 02:45PM

just to be careful:

use carb cleaner to spary head, base, and intake at idle to make sure you have no air leaks.

on your carb, make sure your float is set correctly and engaging / disengaging properly.

Get a new plug, run on WOT for a few minutes....shut the bike off at WOT, pull over and do plug test. What color is it?

That is going to tell you whether you are fine, need to up or downjet.

If you are fine at WOT, then you mess with your needle so that you can fix your other ranges.

MOPED ARMY

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