NC30 low rpm problems
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Please can you post items for sale or wanted in the correct For Sale section. Items / bikes for sale here will be removed without warning. Reasons for this are in the FAQ. Thanks
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jamesrm
- Settled in member
- Posts: 14
- Joined: Mon Jun 30, 2014 6:21 pm
- Bike owned: 89 VFR 400
- Location: North London
NC30 low rpm problems
Hi guys, having a few problems with my 89 NC30 and have tried a few things but have ran out of ideas so seeking some advice!
Problems started a few weeks ago when the bike was running well, then all of a sudden dropped what I believe is 2 cylinders at low rpm/idle only for all 4 to return at wider throttle openings.
So thinking perhaps this might have been some sort of blockage in the carbs I took them off and found them to be in surprisingly clean condition, running 118/120 main jets and everything as per standard settings.
I blasted everything through with carb cleaner and then compressed air, and have since reassembled with new NC35 rubbers only to find identical running problems
it does appear I am getting spark, I don't have any spare plugs to get check, but I can hear the plug lead clicking away if I pull it off whilst running, and it doesn't seem like its any specific cylinders as before the rears were lukewarm heat, but today it seems the left front wasn't producing much heat.
I tried running the engine with the airbox off spraying carb cleaner direct into the carbs and it did seem to bring back 4 Cylinders.
One thing I did notice was the vacuum hose that connects to the fuel tap didn't look that well secured Where it attaches to the cylinder head.
I thought I might have struck gold as it would make sense that leaking vacuum might not bring enough fuel down into the carb at low rpm and starve the engine, conversely at higher engine speeds the increased vacuum might make this less of a problem, but I tried securing more solidly with a cable tie(didn't have anything better at the time) but has made no difference (should their be a jubilee clip as standard?)
Hopefully this information might give some clues to others as not knowing a huge amount about carbs I'm lost!
thanks for reading
Problems started a few weeks ago when the bike was running well, then all of a sudden dropped what I believe is 2 cylinders at low rpm/idle only for all 4 to return at wider throttle openings.
So thinking perhaps this might have been some sort of blockage in the carbs I took them off and found them to be in surprisingly clean condition, running 118/120 main jets and everything as per standard settings.
I blasted everything through with carb cleaner and then compressed air, and have since reassembled with new NC35 rubbers only to find identical running problems
it does appear I am getting spark, I don't have any spare plugs to get check, but I can hear the plug lead clicking away if I pull it off whilst running, and it doesn't seem like its any specific cylinders as before the rears were lukewarm heat, but today it seems the left front wasn't producing much heat.
I tried running the engine with the airbox off spraying carb cleaner direct into the carbs and it did seem to bring back 4 Cylinders.
One thing I did notice was the vacuum hose that connects to the fuel tap didn't look that well secured Where it attaches to the cylinder head.
I thought I might have struck gold as it would make sense that leaking vacuum might not bring enough fuel down into the carb at low rpm and starve the engine, conversely at higher engine speeds the increased vacuum might make this less of a problem, but I tried securing more solidly with a cable tie(didn't have anything better at the time) but has made no difference (should their be a jubilee clip as standard?)
Hopefully this information might give some clues to others as not knowing a huge amount about carbs I'm lost!
thanks for reading
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magg
- Senior Member
- Posts: 1916
- Joined: Mon Sep 20, 2010 11:55 pm
- Bike owned: VFR400
- Location: Blue Mountain NSW Australia
Re: NC30 low rpm problems
There should be a wire spring clip on each end of the vacuum hose. Is the hose in good condition such that there is full fuel flow from the tap when you suck on the hose. If you can suck air through the hose then the diaphragm is faulty.