Clone won't idle after switching to big pipe

C

criderracing

Member
Switched from wienie pipe to big pipe and now it won't idle. Gotta leave the choke 1/3 on to get it to idle. Anybody got any ideas? Could it be jetting?
 
Id def say you need a larger main jet or drill yours. We do this with the predators at our track when we change to afternarket airbox n pipe. Sorry forgot the actual specs on them. A quick search of the forum should yield results. Also did you put an aftermarket air filter on it? Best to do both these engines just need to breathe
 
criderracing said:
Switched from wienie pipe to big pipe and now it won't idle. Gotta leave the choke 1/3 on to get it to idle. Anybody got any ideas? Could it be jetting?
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to clarify here, you changed from weenie pipe and stock airbox, to a big pipe and aftermarket filter correct? If this is the case, you are too lean on your jetting and you need to richen it up, or go to bigger jets. The main reason i say your too lean, is because you have to have the choke part-way on to get it to run and idle. I would go up at least a couple of jet sizes on the main and low speed jet both. Around here when we go from stock airbox and weenie pipe to big pipe and air filter, i have to change from stock 28 main and 19 low speed jets to a .22 or .24 low speed jet and .036 to .039 main jet. Id say if you put a 36 or 37 main jet and .22 low speed jet in it, it will clear up and run good. Fine tune the idle mixture screw on the carb if there is one so you can get the idle right.
 
I have not had one to not with the bolt on changes, but they wont rev without the choke closed some until jetted. The only time I have had them not idle, they needed cleaning. JMO
 
Not to open a can of worms but I have a bone stock one and added a header and muffler and after market air filter adapter too
and it runs just fine wont skip a beat.never touched the stock jets.the header I used is from ARC the J930 so don't what to start
a war about all this but some times I think its just a lot of hype to sell more parts.
 
Iv noticed some engines come stock with bigger jets than others, such as the BSP engines. Every BSP engine i have got new has came with a .036 main jet, not sure what size low speed jet, but the other clone motors like ducar and dupor engines iv had all came stock with a .028 main jet i believe. Could be that you (modifiedman) have a BSP engine, and has .036 main jet stock? I have never been able to get an engine to run as good with stock jets when switching to big pipe and air filter adapter, always had to rejet.
 
modifiedman said:
Not to open a can of worms but I have a bone stock one and added a header and muffler and after market air filter adapter too
and it runs just fine wont skip a beat.never touched the stock jets.the header I used is from ARC the J930 so don't what to start
a war about all this but some times I think its just a lot of hype to sell more parts.
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I did a test with an out of the box predator. I swapped to a header, and it ran fine with the carb untouched. I swapped to a good air filter adapter and it wouldn't run very well at all. It would crank, idle fine, but when I went to make a pull it, well it just wouldn't..I went up to I believe a .021-.035 jet combo, and it did well. Not trying to argue, just what I found.
 
modifiedman said:
Its all good and this is how others learn.now do same thing with air filter off ?
and see what you get.
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I don't understand the last? I have actually ran my best engine with and without an air filter, with and without a outerwear (both Outerwear brand and BSP) with no difference in performance. Is that what you see as well?
 
I guess what I am saying is some k&n filters I have found restrict air flow don't know why and this acts like its starving for fuel
or over chocked.remove it and engine runs fine.just like some say the stock air box and air filter is a restriction.
same as the stock muffler.take it off change it over for better flow and engine runs good. I could be way wrong in my thinking
and have been in the past.also a over oil filter will act the same way,I don't oil mine.and yes I have also done what you have too.
oh and this is one of the older HF blue that I had.I later tested this on a stock Honda gx200 worked just fine luck maybe ?
Now I do have some out of the box with all stock parts still on and do stumble and then have to open up the stock jet some.
had to do this on a couple customers motors but not racing motors.power washers and log splitters.
 
modifiedman said:
I guess what I am saying is some k&n filters I have found restrict air flow don't know why and this acts like its starving for fuel
or over chocked.remove it and engine runs fine.just like some say the stock air box and air filter is a restriction.
same as the stock muffler.take it off change it over for better flow and engine runs good. I could be way wrong in my thinking
and have been in the past.also a over oil filter will act the same way,I don't oil mine.and yes I have also done what you have too.
oh and this is one of the older HF blue that I had.I later tested this on a stock Honda gx200 worked just fine luck maybe ?
Now I do have some out of the box with all stock parts still on and do stumble and then have to open up the stock jet some.
had to do this on a couple customers motors but not racing motors.power washers and log splitters.
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I got ya, I guess the answer is , there is nothing that works every time...LOL. I do oil my filters, lightly. I use the cheap filters, and haven't had any problems.. yet
 
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