Looking for advice after de restricting an LT50. Basically I removed restrictors,piggy back jet and 3" of baffle and quad ran fine until it got hot then it would bog when trying to increase revs. I have fitted a bigger 70 jet today and although the quad is not bogging now it only uses about 1/4 of the throttle compared to before. Just curious if I need to try a smaller 65 jet or change plug to a ngk bpr-5 which is cooler than the ngk bpr-4 currently fitted ? Only plug I can find in UK is a ngk bpr-5hs so would this be ok to use ? Thanks for any replys .

 

I'm not sure I understand how increasing the main now restricts throttle movement to 1/4???


Did you "read" your plug? Are you running very lean (plug is white instead of cardboard tan)?


I'm asking because at 1/4 throttle you're not really on the main yet...what clip position are you running on the needle?

 

I only ran the quad for a few minutes so have not checked the plug yet. Basically the quad now revs up a lot quicker and seems to be making full power at about 1/4 lever movement and any further than this it does not stall but sounds rough where as before the lever was pushed fully home to make max power. I have read on a google search that the standard plug runs too hot when the quad has had the restrictors removed so to use a cooler bpr-5 instead of the standard bpr-4 so I was going to fit the cooler plug before testing any further . The clip position I removed down one place from standard.Thanks for the reply DD .

 

Can you please ensure the slide is seated correctly in the carb and that the cable is not binding (when idling turn the wheels full left & full right...there should be no RPM change)...


You can also validate correct slide function by removing the air box and either looking in or feeling with your fingers...move the throttle through its range...with no throttle the slide should be almost completely closed and at WOT it should be all the way up...


You shouldn't be getting full power at 1/4 throttle...that's not a safe riding condition...

 

Grabbed a quick 5 minutes on the quad this morning.
Slide is seated correctly and cable is not binding.
However the plug was seized in and after removing it,it was obviously old and seen better days.The plug was also black so definetly over fuelling. I will fit new cooler bpr-5 plug when it comes in morning and try it as it is with 70 jet fitted and if still not running right I will refit the standard jet and see how that goes with new plug fitted,I also have a 65 jet coming to try. Thanks again DD .

 

I'd definitely start at baseline (stock)...curious you're going up in main when it's more likely that you need to go down...factory motors are always jetted fat in the main...


Just remember if you jet down the needle most likely needs to move up and vise versa if you jet up, needle should come down...

 

Update !!
I fitted new cooler plug today (bpr-5hs) and removed 70 jet and refitted standard main jet (57.5) and the quad has been transformed. The quad now starts and screams right up to full throttle and so far after running it in back garden for a while, alternating between tick over and revving it up it has ran fine with no bogging so far. Lesson learned,I had thought that the bogging was a lack of fuel and so increased the main jet when it has more than likely been the standard plug (bpr-4) getting too hot for the unrestricted engine. I have already ordered 60 and 65 jets so will try them once they arrive and will report back .

 

Do you know how to do a plug chop? It will help you to jet the main...

 

I dont DD but im keen to find out if you dont mind explaining it to me. Thanks again .

 

ok...here goes it:
1) let machine warm up
2) find long stretch
3) fly down the stretch at WOT (wide open throttle)
4) Kill the engine - then release throttle (while flying down stretch)
5) pull the plug and read the electrode area (running well would be a cardboard brown color, lean would be light tan to whitish, rich will be dark tan to blackish)


I personally run on the richer (darker) side...not black, but darker than cardboard color (to account for leaner conditions when the weather turns colder). Once you get the main nailed down you can do the same to get an idea where you are with the needle at part throttle positions. I usually test WOT and 1/2 throttle. But you need to do the main first as changing that impacts all other throttle positions above 1/4...


Hope this helps!