Gas n Spark - Still Won't Start

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SoCalBoy

New Member
Aug 20, 2015
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Southern Calif
After putting a few hundred miles on my 4 cycle 142 hs, I decided to put a long header exhaust and UNI air filter on it to help it breath better and hopefully give me a little more umpf.

After reading this: http://www.affordablegokarts.com/49cc-high-flow-air-filter.php I drilled out my jet with a #71 drill bit, thinking that because I'm using the very same filter, I could cut to the chase and skip all of the incremental steps of increasing the jet size one step at a time.

My question is: could this jet be so large now that it's flooding the engine, not letting it start?

As the title says, the engine has spark and gas. Please help... I just don't know what I should do next. Thanx...
 

SoCalBoy

New Member
Aug 20, 2015
15
0
1
Southern Calif
Thank you Venice...
At first I did. Later, after thinking that the jet might be too large, I tried without the choke. Nothing seems to help.

Hopefully, more people will respond to this - perhaps some that have lots of experience with rejetting after mods such as mine...

Thanks again...
 

2door

Moderator
Staff member
Sep 15, 2008
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Littleton, Colorado
If you suspect the problem is the jet it isn't difficult to solder the jet closed ad re-drill to the original size. Goint back to square one is always a good idea when you encounter a problem with a modification. Also when doing mods, do one at a time. That gives you some basis for comparison.

I doubt your problem is flooding from excess fuel but I'd want to know how the spark plug looks after an attempt to start the engine. Is it wet?

Did you make any other changes other than going larger on the jet?

Tom
 

curtisfox

Well-Known Member
Dec 29, 2008
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minesota
I think you may have air leaks if the plug is not wet, if its dry put some gas in the plug hole and try starting it. If it fires you may have air leaks,gasket or something bad...............Curt
 

MotoMagz

Well-Known Member
Aug 2, 2010
1,817
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When I had my lil 4stroke I had a problem that started all the sudden after a ride..it was the kill switch. Unhook it and try starting it if all else fails...good luck
 

SoCalBoy

New Member
Aug 20, 2015
15
0
1
Southern Calif
If you suspect the problem is the jet it isn't difficult to solder the jet closed ad re-drill to the original size. Goint back to square one is always a good idea when you encounter a problem with a modification. Also when doing mods, do one at a time. That gives you some basis for comparison.

I doubt your problem is flooding from excess fuel but I'd want to know how the spark plug looks after an attempt to start the engine. Is it wet?

Did you make any other changes other than going larger on the jet?

Tom
Thank you all for your help on this...

Tom... After waiting 24 hrs, then trying to restart withOUT choke, I got one backfire, then nothing after 8 or 9 pulls. Removed the spark plug and yes, it was wet. This, I believe, confirms that I drilled out the jet too large. I've never soldered a jet before, and I don't have much in the way of tools like a vice and drill press, just simple hand tools. Any tips/advice on how to do the solder right?

As to "other changes"... After installing the UNI filter and BBR Tuning 4-Stroke Long Shot Extended Exhaust Muffler Pipe, the only "other changes" I made was drilling out the main jet; nothing more.

I really appreciate everyone's help... Thank you ALL...
 

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
SoCal,
Here is a link to a very crude tutorial I did on soldering and drilling carburetor jets.
https://www.youtube.com/watch?v=GcYd97t-6ns

The only problem I think you'll have is not knowing the original size of your jet. In this video I mention that as the first step so you'll have a base line to go from.

I persoanlly don't know the stock jet orifice size of your engine but maybe someone here can tell you.

I typically mention when discussing jet size that there are a lot of inconsistencies between vendors and what they sell. This is particularly true with the 2 stroke carbs. I don't rely on published 'jet size' or 'jet numbers' but use wire drill size which is consistent across the board. Others might have differing opinions.

Let us know what you find and I'd suggest you assure the ignition system is functioning properly. This usually isn't a problem on the 4 stroke engines but it isn't unheard of. The suggestion to check or disconnect the kill switch is a good one. Try that.

Tom
 
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