So i got the mod honda to the track yesterday for the first time this year. I had a 175 jet, it was 60-65 degrees and i was way way rich. Get on it coming out of a corner and blah. Pull the clutch, let it catch up and it would accelerate at least and start it all over. I have run this size in the past with no issues when cold out, knowing it was rich. Appeared to get worse as the engine got a little heat in it.
Would a new fuel pump and floats cause this or do i have another issue?
I did not rebuild the top end and it ran when parked for the winter.
Hard to tell too much about the jetting from here and there are so many things that can affect it. First, how do you know it’s rich? Did you read the plug or piston top? It could actually be lean if it’s causing a hard ‘bog’ out of the corner.
The outside temp does affect the air but, it can be so different from day to day (or hour to hour). A weather gauge is your best friend when trying to set jetting based on air changes. Anyway, if you’re used to running safe jetting and it usually works, don’t worry too much about that right now.
Check your plug to verify jetting and work from there. It could be your pilot, needle, main, pumps, floats etc. Any could cause the problem, but since you mentioned new pump and floats, my guess is:
Fuel pump isn’t working correctly which would mean it’s lean. (this could also be caused by a pinched fuel line or tank pickup problem)
Floats aren’t set (or maybe stuck) and it’s could be lean or rich.
What’s the fuel sitch? Do you know it to be good fresh fuel?
the more I thought about this, I might be back to the same issue I had last year where my return line is too big. thus causing a lean/starvation issue. what is the best/ideal way to reduce the size of the line and what size is expected? I have been running close to fuel line OD with thicker wall tubing. its a little smaller but not by much if at all?
and I do not have a pump around.
fuel is good, picked it up a week or two ago.
floats are new and not stuck as far as I can tell. is 16mm the correct float level? or is it 15?
One thing to make sure of is that your return line loops higher than anything else in the system.
Another cool trick is to go to a auto parts store and ask for a fuel filter for a 1983 Subaru, I like to go to NAPA auto parts and get a Wix 33201 (same thing), you run it backwards using the return for an inlet, the other for the return, and the bottom for feeding the carb.
It basically makes for a $5.00 magic can…
What great idea ! I’m going to used something similar to your innovation on both my Shifters.
One Honda CR125 Shifter has the New Tillotson HM-1A 42mm with a double stack fuel pump that does not require a fuel return line. So on that one I’ll just
use a standard Fram GF12 filter as a mini fuel tank (magic can) directly above the carb upside down to insure a good fuel supply to the Tilly.
The second Honda CR125 Shifter has a Mikuni BN40I 38-27 40mm with its own built in return line system. So again I’ll just use a standard Fram GF12 filter as a mini fuel tank.
Good Racing Bob Horvath
Thanks Robert Horvath at
Oconomowoc Wi 53066 U.S.A
Just put a size 200 jet in the return line.
Fought a very similar sounding problem for a long time. Solution: Dellorto fuel pump with no return line. Has an internal 0.5 psig bypass. Problem was created by excessive return volume, w or w/o 200 main jet in the return.
Josh, ill look into a deltoro pump but i just remounted the pump and put the return line at a larger angle vs inlet. WoRked so far.