blauth
Race Dog
I'm struggling with jetting and perhaps someone can help.
I've got a 1998 Honda XR600R, in great shape with just over 17000km on her. It's got the standard pipe without baffle and air filter is aftermarket with snorkel removed from airbox. It runs really strong on acceleration and top end (she'll run to the end of the clock on all but the steepest hills) BUT ..... and there's always a but. I've started doing some commuting on it for lack of another running bike and when I have my throttle at less than 1/8th open and the engine is not under load, like when I'm sifting between the cars, it surges, horribly so there's a lot of clutch action to try keep the bike smooth. This condition is hardly noticable on normal riding conditions like when riding offroad or if there is no traffic.
The idling appears to be fine and the bike starts very easily (hot and cold[with choke]). First kick if I pay attention else second kick or worst case third when I'm kicking like an ass.
- Carb has been cleaned.
- Pilot jet: currently 62. I've tried 55, 58 as well, no better, possibly worse. The bike returns to idle correctly when the clutch is pulled in.
- Main jet: 155 which I think is about right. I tried a 152 but it became flat on the top end.
- Needle position: Middle clip. I tried raising the needle one clip (second slot from bottom) to richen the mid range but it made the problem worse.
- Float level is set to the recommended 14.5mm.
- Air screw is 2 turns out. The 0-ring was buggered so I put another in (it's a little small though so not sure if it's working properly). I can't believe the air it would suck past the thread would cause this much of a problem though.
- The Air Cutoff Valve membrane appears to be in good condition.
- The chole appears to be properly open.
This problem appears to be particularly bad when opening up just after over-run (like on a downhill). It even surges slightly while in the over-run (clutch out) when the throttle is closed and almost wants to run on.
I've checked the valve clearances (0.1mm on inlet and 0.13 on exhaust)
I've made sure there is slack in the decompression lever cable which I never use anyway.
Accelerator cable is not too tight, there is a small amount of free play before the cable actions the slide.
I don't really know what else to try. I can only assume it's got something to do with the pilot circuit or perhaps the Air Cutoff Valve(ACV). I'm maybe going to temporarily disable the ACV to see what effect that has on the bike, I suspect it will be a balls up.
Any other suggestions?
I've got a 1998 Honda XR600R, in great shape with just over 17000km on her. It's got the standard pipe without baffle and air filter is aftermarket with snorkel removed from airbox. It runs really strong on acceleration and top end (she'll run to the end of the clock on all but the steepest hills) BUT ..... and there's always a but. I've started doing some commuting on it for lack of another running bike and when I have my throttle at less than 1/8th open and the engine is not under load, like when I'm sifting between the cars, it surges, horribly so there's a lot of clutch action to try keep the bike smooth. This condition is hardly noticable on normal riding conditions like when riding offroad or if there is no traffic.
The idling appears to be fine and the bike starts very easily (hot and cold[with choke]). First kick if I pay attention else second kick or worst case third when I'm kicking like an ass.
- Carb has been cleaned.
- Pilot jet: currently 62. I've tried 55, 58 as well, no better, possibly worse. The bike returns to idle correctly when the clutch is pulled in.
- Main jet: 155 which I think is about right. I tried a 152 but it became flat on the top end.
- Needle position: Middle clip. I tried raising the needle one clip (second slot from bottom) to richen the mid range but it made the problem worse.
- Float level is set to the recommended 14.5mm.
- Air screw is 2 turns out. The 0-ring was buggered so I put another in (it's a little small though so not sure if it's working properly). I can't believe the air it would suck past the thread would cause this much of a problem though.
- The Air Cutoff Valve membrane appears to be in good condition.
- The chole appears to be properly open.
This problem appears to be particularly bad when opening up just after over-run (like on a downhill). It even surges slightly while in the over-run (clutch out) when the throttle is closed and almost wants to run on.
I've checked the valve clearances (0.1mm on inlet and 0.13 on exhaust)
I've made sure there is slack in the decompression lever cable which I never use anyway.
Accelerator cable is not too tight, there is a small amount of free play before the cable actions the slide.
I don't really know what else to try. I can only assume it's got something to do with the pilot circuit or perhaps the Air Cutoff Valve(ACV). I'm maybe going to temporarily disable the ACV to see what effect that has on the bike, I suspect it will be a balls up.
Any other suggestions?
