Yamaha Malta won't idle

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RIBW

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I have renewed the spark plug, stripped the carb and used carb cleaner everywhere, tightened the flange nuts.
Still it won't idle.
Has anyone any suggestions for on-boat fix?
(Otherwise, it will go home to be fixed in slow time)
Cheers
Bob
 
There have been a lot of similar threads on here recently including from me. Mine's with the Honda agents at the moment. The most likely culprit is apparently crud in the main jet.
 
Yes, I've had that. The slow running jet is blocked. It sounds bizzare, but boil the carb in a pan of water for about 5 mins. Don't just drop it in, btw, bring it to the boil as you would a hard boiled egg. Strip the carb down removing all the jets, float and carefully remove the gaskets etc. On mine it took 3 boils over a period of days and attempts for it to free. It was an old-timers trick with lawn mowers and small 2 stroke engines.
Mike
 
Vegable said:
Yes, I've had that. The slow running jet is blocked. It sounds bizzare, but boil the carb in a pan of water for about 5 mins. Don't just drop it in, btw, bring it to the boil as you would a hard boiled egg. Strip the carb down removing all the jets, float and carefully remove the gaskets etc. On mine it took 3 boils over a period of days and attempts for it to free. It was an old-timers trick with lawn mowers and small 2 stroke engines.
Mike
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These days it's better to ultrasonically clean the carb.
Not sure how the float might react to being boiled, best to strip the carb fully?
If it's not the carb, it could be an air leak between the carb and engine, crankshaft seals, choke maladjusted etc.
 
lw395 said:
These days it's better to ultrasonically clean the carb.
Not sure how the float might react to being boiled, best to strip the carb fully?
If it's not the carb, it could be an air leak between the carb and engine, crankshaft seals, choke maladjusted etc.
Click to expand...

Don't put it in boiling water. It has a diaphragm in it and will knacker it. You pilot jet and or transition ports are blocked.
 
Still none the wiser are you? Probably even more confused. Forumitis strikes! I have a Yam 2.5 and did all the usual for a similar problem. Turns out that 9 times about of 10 after stripping you need new gasgets. They are not like the old ones ! Bite the bullet -- £££ and it will go again.
 
My malta also had a gauze filter in the fuel tap, so check that out as well. New gaskets as mentioned or gasket sealer is worth using as well. The other option is that when I head west later this year we meet up and you give me the Malta !
 
Thanks again to all. Its going in the car this morning and heading for the bench!
I had new gaskets in mind 'cos of the possibility of an air leak.
Cheers
Bob
 
Ludd said:
Most usual problem is the emulsifying tube blocked.
Click to expand...

On tick over the emulsion tube or main jet doesn't actually do anything. As I stated before your problem is in the slow running circuit. Either pilot jet or transition ports. Do not use gasket sealer any where near a carb. I have a scrap Malta carb in the workshop. I will have a look in a minute
 
Malta Yamaha , Yamaha 2.5 all have a carb problem and need to be careful put away before the winter set in , I just got an Yamaha 2.5 from a friend that had a carb problem , it now been strip out over 30 times each time starting first time , run half an hour then stopped again , carb clearer , and lots of blowing didn't make any different ,
and at last fingers cross the problem solved , I think :) , only time will tell .
The port are so small that just normal cleaning and blow out don't always do the job , if you can , get it sonic clean , it will say you lots of time .
gasket , need to be change , if you happen to be somewhere you can't get new gasket , buy some gasket paper and make one ,next best thing to gasket paper if you can't get hold of any is wet and dry paper very very fine , wet it rub the grit away , let it dry then cut out the gasket .
Card wil also do the trick to get you out of trouble .
 
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Take off the top plate held on by 2 screws. You will see 2 black bungs. One oblong and one round. The oblong one contains 2 jets. Clean them in situ. The round one has transition ports underneath. Make sure the port holes are clean. Unscrew the slow running jet and give that a blast out too. One and a half turns from stop is usually about right when you reassemble. Check the carb gasket when reassembling. If bad makes new one from a cornflake box until you get home.
Steve
 
sailaboutvic said:
......I just got an Yamaha 2.5 from a friend that had a carb problem , it now been strip out over 30 times each time starting first time , run half an hour then stopped again , carb clearer , and lots of blowing didn't make any different ,
and at last fingers cross the problem solved , I think :) , only time will tell .
Click to expand...
Hi,
On a charter many years ago I went through 3 Y2.5s in a week but that was the 4 stroke machine I agree - a real pain!
Bob
 
steve66 said:
Take off the top plate held on by 2 screws. You will see 2 black bungs. One oblong and one round. The oblong one contains 2 jets. Clean them in situ. The round one has transition ports underneath. Make sure the port holes are clean. Unscrew the slow running jet and give that a blast out too. One and a half turns from stop is usually about right when you reassemble. Check the carb gasket when reassembling. If bad makes new one from a cornflake box until you get home. Steve
Click to expand...

Steve,
Thanks so much for that - a great help.
Removing the black plastic plug was a step too far on a gusty pontoon, as was that top cover! The engine is now back in my garage and I'll have go at these items tomorrow. (The pilot did come out and is clear).
It hasn't helped that I haven't found any diagrams for the various phases in the carb - (I have full colour diagrams for our spare engine - a treasured Yamaha/Mariner3.5AC from 1975 with only 10 hours in the water!)
Cheers
Bob
(Also now back on broadband)
 
RIBW said:
Steve,
Thanks so much for that - a great help.
Removing the black plastic plug was a step too far on a gusty pontoon, as was that top cover! The engine is now back in my garage and I'll have go at these items tomorrow. (The pilot did come out and is clear).
It hasn't helped that I haven't found any diagrams for the various phases in the carb - (I have full colour diagrams for our spare engine - a treasured Yamaha/Mariner3.5AC from 1975 with only 10 hours in the water!)
Cheers
Bob
(Also now back on broadband)
Click to expand...

Bob , also check the tank and fuel pipe from the tank .
You can also try removing all the jet and dia from the carb and soak it in warm vinegar over night .
The minuscule spot of crap will cause you problem on these carbs , so blowing it and poking soft wire thro won't guarantee clean ports .
Example , I had mine running at full speed in gear moor to our yacht for an hour , thinking I sorted the problem shot off for supply only for it to stop again on the way back , good news now is after five days it still working ,
 
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