What a difference a carb makes!

Street Ryderz

Well-Known Member
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Joined
Oct 14, 2016
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4,473
Location
Ft Erie Ont
The orange 29er I built a custom Road Runner engine for and hung a custom pipe on for another local builder was having issues getting dialed in after break in the bike ran nice and smooth in the botom end and I could get a nice idle but it was fat while still on the needle.I told him the main jet now needed changed and should be good he said he would do it and took the bike,two days latter he rolls in and says it wont even climb hills now,Ok so itake it for a ride it starts right away and has normal initail pull then as I roll in the throttle it starts to climb in r's and goes fat again so of course if you persist in giving it throttle it bogs out some and makes no power apon my return I ask if he rejetted it,no he said the shop he goes to didnt have the jet in the smaller # sizes,so ok something changed though it like your running on the pilot jet I dont know he tells me lol.sure enough the air screw is dialed out past two turns I put it back to the 3/4 turn I had previously set it at knowing thats not right etheir but was the best for now.When this engine was commisioned I told the guy he would need a bigger better carb for it and he told me he was going to use the cns carb that I was previously using because he had one allready not bored out like mine but a new stock one to work with well the cns carb that was put on is not the same as the one I used at all.The intake side and the venturi side are completly different the valving all different the bore ONLY 14mm wtf I didnt notice any of these at first glance when it was installed except that the venturi area and air filter where odd but after looking at it properly and realizing that this carb was strickly for a stock set up I called him in and showed him what it was and said I put my cns carb that is bored out to 18mm has the idle jet drilled out so the air screw could be set to one and a half turns out and get good idle and that engine seems to work well with a #78 in the carb for the crispy responcive feel but I suggested an 80 for mid summer use dought he'll do it but now it screams through the gear and needs a smaller one lol The first three pic's are the small one the others are a stock 16mm one
 

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