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Hot Starting Problem
Posted:
Sun May 19, 2019 8:09 pmby LammySX
Hi, I am posting here as I think I have a carburetor/fuel problem.
Scenario
A modified SX200 starts first or second kick every time
After about 30/40 mins of riding if I switch off 9 times out of 10 it won't start. If switch off petrol and leave it half an hour and it starts on the first kick.
Very difficult to maintain tickover, always have to keep the revs up at traffic lights or it will die and I'll be stuck there for half an hour (;-) Sometimes I miss it and it dies, like a fuel starvation problem.
Initially thought it was flooding and got into the habit of switching off fuel for a few minutes before cutting the engine. Seemed to work for a while.
Stripped the carb, cleaned everything and blew jets with compressed air. Replaced float and a new red tip needle which was 1/32" longer than the one I took out. That seemed better but it's now gone back to a difficult hot start.
Drained the tank and cleaned all the crud out, measure flow 200ml per minute.
I am now thinking fast flow tap or new carb.
BTW if I am lucky enough to stop on a decent hill it bumps every time.
I am not thinking electrics at the moment
Any other suggestions?
Thanks
J
Regards
J
Re: Hot Starting Problem
Posted:
Sun May 19, 2019 8:23 pmby MickYork
A few options, but all carb' related.
You're trapping fuel in your bellows and flooding. Some bellows have a drain on them to help overcome this.
Your pilot may be too large and/or your choke may be sticking and/or air filter may be blocked
90% sure it's carb' related.
Re: Hot Starting Problem
Posted:
Sun May 19, 2019 10:18 pmby LammySX
MickYork wrote:A few options, but all carb' related.
You're trapping fuel in your bellows and flooding. Some bellows have a drain on them to help overcome this.
Your pilot may be too large and/or your choke may be sticking and/or air filter may be blocked
90% sure it's carb' related.
It does have a drain and the choke sticking and or too large a pilot was my next options. Air filter is new
Is there any guidance available on choke adjustment/maintenance i.e. how would I know if it's sticking
Re: Hot Starting Problem
Posted:
Sun May 19, 2019 10:42 pmby rossclark
With the hose off you should be able to see the plunger lift / drop by looking down the front of the carb as you pull the cable. You need to make sure it closes off properly when shut and that the cable has a mm or two of slack before it operates off the lever.
Re: Hot Starting Problem
Posted:
Sun May 19, 2019 11:02 pmby CHRIS in MARGATE
I assume it is a SH1/20 or perhaps 22mm Jetex.
First question:
Has it always done this or did it just suddenly start?
What modifications to the SX200?
Silly fixes but try a new spark plug. Take the fuel cap off.
Have you by chance fitted an inline fuel filter.
Your rings might be worn. You need a compression test.
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 12:02 amby Fast n Furious
Could also be an air leak on the inlet side. This would also explain lousy tickover.
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 7:29 amby LammySX
CHRIS in MARGATE wrote:I assume it is a SH1/20 or perhaps 22mm Jetex.
First question:
Has it always done this or did it just suddenly start?
What modifications to the SX200?
Silly fixes but try a new spark plug. Take the fuel cap off.
Have you by chance fitted an inline fuel filter.
Your rings might be worn. You need a compression test.
Always done it, no modifications, new plug fitted, no filter, fuel cap off makes no difference although I can't see any visible signs of a breather I believe there are two types.
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 7:29 amby LammySX
rossclark wrote:With the hose off you should be able to see the plunger lift / drop by looking down the front of the carb as you pull the cable. You need to make sure it closes off properly when shut and that the cable has a mm or two of slack before it operates off the lever.
Thanks, I'll take a look.
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 10:05 amby Rich Oswald
If it is none of those, I am thinking worn rings,
Rich'
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 12:23 pmby LammySX
LammySX wrote:Hi, I am posting here as I think I have a carburetor/fuel problem.
Scenario
A modified SX200 starts first or second kick every time
After about 30/40 mins of riding if I switch off 9 times out of 10 it won't start. If switch off petrol and leave it half an hour and it starts on the first kick.
Very difficult to maintain tickover, always have to keep the revs up at traffic lights or it will die and I'll be stuck there for half an hour (;-) Sometimes I miss it and it dies, like a fuel starvation problem.
Initially thought it was flooding and got into the habit of switching off fuel for a few minutes before cutting the engine. Seemed to work for a while.
Stripped the carb, cleaned everything and blew jets with compressed air. Replaced float and a new red tip needle which was 1/32" longer than the one I took out. That seemed better but it's now gone back to a difficult hot start.
Drained the tank and cleaned all the crud out, measure flow 200ml per minute.
Update
I should have said, last week it was running at very high revs when I stopped. I didn't do anything, it resolved on its own
I am now thinking fast flow tap or new carb.
BTW if I am lucky enough to stop on a decent hill it bumps every time.
I am not thinking electrics at the moment
Any other suggestions?
Thanks
J
Regards
J
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 12:23 pmby LammySX
I should have said, last week it was running at very high revs when I stopped. I didn't do anything, it resolved on its own
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 7:18 pmby LammySX
MickYork wrote:A few options, but all carb' related.
You're trapping fuel in your bellows and flooding. Some bellows have a drain on them to help overcome this.
Your pilot may be too large and/or your choke may be sticking and/or air filter may be blocked
90% sure it's carb' related.
Pilot is 48, that's standard - is going any lower beneficial?
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 7:25 pmby MickYork
With the high revving it sounds like an air leak, definitely worth investigating.
Drop the size of the pilot, but plug chop and check you're not too lean. You can always go back to 48.
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 9:27 pmby LammySX
Update
Looking on various threads I see that no throttle is recommended, I tried it tonight. Ran for 30 mins, switched off petrol before the engine and waited 5 mins. Started the first time, repeated the exercise three times with success, feeling chuffed I went for a spin while the sun was out and confidently stopped for the fourth time. Big mistake, couldn't get it started, tried fuel on and fuel off, eventually got it started after about twenty kicks, drove 100yds and it died. Then spent 45 minutes trying to get it started and ringing the RAC and the wife to bring me a plug spanner.
Faced with the prospect of being out in the cold until midnight which was the ETA of the RAC, I tried again with the choke on. It started after about three kicks.
So I have a hot/warm engine that needs the choke, what does that tell me?
J
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 10:21 pmby MickYork
The choke adds more fuel, altering the ratio of fuel to air.......so you have either either too much air (air leak) or too little fuel (bigger pilot jet).
With the over rev' you mentioned previously this would point to an air leak.
An air leak can cause serious problems, with the potential of holing your piston.
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 10:25 pmby CHRIS in MARGATE
If your carb is adjusted correctly and your engine is revving too high at tickover and is slow to return to idle then you most definitely have an overly weak mixture that is more often than not caused by an air leak.
Your initial posting stated that you had a modified SX 200.
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 11:21 pmby LammySX
CHRIS in MARGATE wrote:If your carb is adjusted correctly and your engine is revving too high at tickover and is slow to return to idle then you most definitely have an overly weak mixture that is more often than not caused by an air leak.
Your initial posting stated that you had a modified SX 200.
Hi Chris, it's definitely unmodified , that was a mistake (;-)
I'll need to look at the air leak possibility
John
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 11:23 pmby LammySX
MickYork wrote:The choke adds more fuel, altering the ratio of fuel to air.......so you have either either too much air (air leak) or too little fuel (bigger pilot jet).
With the over rev' you mentioned previously this would point to an air leak.
An air leak can cause serious problems, with the potential of holing your piston.
Hi Mick, are you suggesting smaller or bigger pilot?
Re: Hot Starting Problem
Posted:
Mon May 20, 2019 11:27 pmby LammySX
Where would I start to look for an air leak?
Re: Hot Starting Problem
Posted:
Tue May 21, 2019 12:31 amby rossclark
you need to do a leak down test, basically find a means to pressurise the cylinder and crankcase and see how long it holds pressure for.
A simple way to do it is with the piston at BDC place a section of bicycle inner tube with one end over your carb manifold and the other over the end of your exhaust U bend. Pump it up to about 5 psi and see if it holds - if not start spraying soapy water round the various joints - inlet manifold, cylinder head, base gasket, round the mag housing etc.