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medicallen
07-23-2007, 07:39 AM
I am needing some advise, I have an 04 with some mods, hetrick pipe, 24mm carb, uni filter, it is a 52mm bore I just put a fresh piston and rings in it and now it will idle fine, but if you give it past 1/4 throttle it cuts out and backfires and won't hardly run, but it goes right back and idles fine. If you go straight to full throttle it bogs and dies? I've tried plug, reeds, and cleaned the stator. Anyone got any suggestions?

gr race
07-23-2007, 08:46 AM
should have put a B-52 cylinder on!!!:devil:

Nichols Atvs
07-23-2007, 08:54 AM
if its an new carb try going up alittle on your air pioletj et or change your jetting ,what color is your plug should be a tan color in the center if its black its to rich if its to white its to lean may need to adjust your needle up or down to go richer or leaner allso tell us alittle more info after you checkout main jet size to give you which way to go on that up or down in size. Carb could be dirty if it older .

medicallen
07-23-2007, 08:58 AM
I sure wish I could have put that B 52 on it..

It's the same jetting that was working great before I changed the piston and rings, plug looks good. Have had the thing running good for a year untill I changed the piston and rings. I did go from a 54mm cylinder to this 52, could something be wrong with the cylinder, also running the same head.

gr race
07-23-2007, 09:12 AM
Hate to kick a man when he's down just could'nt resist. It diffenity shoulds like a fuel issue

medicallen
07-26-2007, 07:32 AM
Well I finally got to mess with the little bike some, put a compression tester on it and it had about 85psi of compression, with new piston and rings and cylinder honed? Not sure what's up with that.

markvette
07-26-2007, 08:25 AM
could be too much squish between the piston and head, also the 54mm head is not helping you on a 52mm cylinder

medicallen
07-26-2007, 02:21 PM
It has a 52mm head changed that too. Anyways explain too much squish, and how do you correct that?

markvette
07-26-2007, 05:58 PM
that is the space between the piston and head at top dead center. to measure use solder, bend in L shape, insert in spark plug hole, turn motor to compress solder. if the motor turns all the way over with no resistance when the piston hits the solder the solder is not thick enough. anyway the piston should stop when it hits the solder, turn it the rest of the way over to squish the solder. take the solder out and measure with a digital set of calipers.. i like my squish between .020 and .035. if it is like .070 or bigger then that is why the compression is so low. you can get thinner base and head gaskets to reduce the squish. you would need to measure what you have on it now to know what size you would need to reduce the squish. wrh racing has any thickness head and base gasket you would need.

Mark

medicallen
07-26-2007, 08:05 PM
Cool I will check that when I get off work on Sat. I have heard of the squish before but never knew exactly what it meant.

markvette
07-27-2007, 08:09 AM
you can buy rolls of solder at a hardware store. i usually by a roll of 2 different thickness. each cylinder can have a different deck height. i have measured 2 cylinders of the same brand and there be a mm of difference in them. could go the old poor mans port job route but that gets a little complicated. thats where you have the cylinder decked and add a spacer plate and 2 base gaskets to the bottom of the cylinder. that way you get higher compression and raises the ports up for better port timing. most stock cylinders the ports are partially closed when the piston is at tdc so raising the cylinder puts them closer to where they should be.

Mark