4,346 posts in this topic
I've been trying to work out this low speed jetting issue for a while now and am running into some weird problems. It seems like most of the bikes I see with this mod are running either a 42 or 45 pilot and now I'm sitting at a 55 and still having lean running issues. The bike will cough through the carb at less than 3 turns under 1/4 throttle on fuel screw. Above 3 turns it will run fine off idle but the idle sometimes hangs.
As the bike sits it's running 55 pilot, 85 pilot air jet, ELT needle (NCVT equivalent) three clips from the bottom, and 165 main jet. Above 1/4 throttle the bike runs like a champ and pulls hard throughout the rpms/throttle position.
With the 55 pilot I can set the fuel screw ~3 turns out and I won't get any cough back through the carb under 1/4 throttle but it has problems with the idle hanging intermittently. Anything above 3 turns out and the idle starts to drop and the bike will stall. I'm around 500 above sea level.
Carb has a new vacuum release plate o-ring, completely cleaned out, hot start air ports rtv'ed shut, rd powerbowl 2. Another thing is I bought the carb missing the whole tps sensor (might be an issue) but I tested the open part where it should be by spraying propane at the opening and had no change in idle speed.
I've got a 58 pilot on order but it just seems like that's big compared to everyone else. Any advice would be appreciated!
Can anyone explain to me why the mid-pipe on certain XR600R/XR650L exhausts gets substantially bigger before attaching to the muffler? In most cases it is actually the same size as the muffler where it attaches. The XR's only mufflers are a great example of this and so is my White Brothers E series muffler. On the other hand you have the more traditional mid-pipe shape from companies like FMF for the same XR600R. The midpipe is relatively the same size from the header to the muffler connection. Even high performance street bikes use this approach so why is it different with the big single?
I've been looking at replacing my White Brothers muffler lately because it doesn't have the discs nor the backing plate to make it USFS approved. I've been back and forth between the FMF Powercore 4 and the xr's only mufflers. I was wondering if the odd mid-pipe shape helps the XR's only mufflers flow better. From what I've read the XR's only mufflers are stupid loud and that would warrant a quiet insert for me and thus choking the high flow muffler, right?
Also, for anyone wondering- the White Brothers header that was installed on my XR600R is VERY CLOSE to the same dimensions as an XR's only header at both the cylinder and mid-pipe connection.
Hey guys, Just came across all of these old school slide shows. They take awhile to record and upload to youtube. But I'm trying to get the good ones done first. Full of info and fun to watch. This one is all off road models cr500r cr250r cr125r cr80r cr60r as well as xr200 xr250 and xl600r. Also there is a test at the end of part 2 so make sure you study hahah.
I'm about to do another from 84 street bikes going to be fun