Aussiedrew
New Member
Hi guys.
I've had my CB400N scrambler running on VM30's for about 3 years now and everything about the carbs is awesome. Great throttle response, smooth idle, NO off idle hesitation, pulls much harder through the low, mid and top end than the standard CV carbs (which never ran well on pods anyway). I dialed them in myself and have made a few tweaks over the years to get them exactly spot on.
However, there's one thing that no matter what I try, I cannot get to work and it's the damn enricher/starting circuit! With the enrichers off, the bike won't start when cold but starts instantly when warmed up. Never had a bike start so quickly, the engine literally rotates about once.
So naturally, when cold I need the enrichers. Flick them on. Press the starter and it starts instantly and revs up to around 3000rpm or so (no tacho so just a guess). However, after about 5 seconds the revs will start to drop and the engine will stall as if it's way too rich. If I flick them off before it stalls, the bike will idle for a few seconds then stall because obviously is hasn't warmed up yet and still needs a little richness but the level provided by the enrichers is far far too high! So I get stuck in a cycle of enrichers on, start bike, enrichers off, wait for stall, enrichers on, start bike, enrichers off, wait for stall... This goes on for about 5 cycles until the bike can finally hold idle without needing the enrichers.
I can compensate by richening the idle circuit with larger jets and winding in the air screw which negates the need to use the enrichers but then the bike is way too rich once warmed up and I get the dreaded off idle stumble.
Surely I'm not the only one with VM's who has this problem. I need a way to lessen their effect. They're off/on and have no middle ground. Holding them open 3/4 or 1/2 or 1/4 etc. doesn't help either, it still stalls out.
Here's a picture of my ride. Love it to bits, but 3 years down the track and I still haven't solved this issue.
I've had my CB400N scrambler running on VM30's for about 3 years now and everything about the carbs is awesome. Great throttle response, smooth idle, NO off idle hesitation, pulls much harder through the low, mid and top end than the standard CV carbs (which never ran well on pods anyway). I dialed them in myself and have made a few tweaks over the years to get them exactly spot on.
However, there's one thing that no matter what I try, I cannot get to work and it's the damn enricher/starting circuit! With the enrichers off, the bike won't start when cold but starts instantly when warmed up. Never had a bike start so quickly, the engine literally rotates about once.
So naturally, when cold I need the enrichers. Flick them on. Press the starter and it starts instantly and revs up to around 3000rpm or so (no tacho so just a guess). However, after about 5 seconds the revs will start to drop and the engine will stall as if it's way too rich. If I flick them off before it stalls, the bike will idle for a few seconds then stall because obviously is hasn't warmed up yet and still needs a little richness but the level provided by the enrichers is far far too high! So I get stuck in a cycle of enrichers on, start bike, enrichers off, wait for stall, enrichers on, start bike, enrichers off, wait for stall... This goes on for about 5 cycles until the bike can finally hold idle without needing the enrichers.
I can compensate by richening the idle circuit with larger jets and winding in the air screw which negates the need to use the enrichers but then the bike is way too rich once warmed up and I get the dreaded off idle stumble.
Surely I'm not the only one with VM's who has this problem. I need a way to lessen their effect. They're off/on and have no middle ground. Holding them open 3/4 or 1/2 or 1/4 etc. doesn't help either, it still stalls out.
Here's a picture of my ride. Love it to bits, but 3 years down the track and I still haven't solved this issue.