Hi all<
I can get my bike to fire by squirting fuel into the spark pug hole and the engine fires two or three times, but I can't keep it running. I've stripped the (Amal M76/426) carb and cleaned everything, but no luck.. Any ideas?
thanks,
Chris
350NZ carburetor issues?
Moderator: Mods
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thunderbolt
- Tool Cleaner
- Posts: 52
- Joined: Fri Aug 14, 2015 2:49 pm
- Location: England
Re: 350NZ carburetor issues?
Is the needle position o.k.? The jet is really clean? The fuel should not be too old. When I start my NZ after a long times, it takes several kicks, till the fuel is in the cylinder. Maybe you must just try more often. Good luck.
Re: 350NZ carburetor issues?
Hi Chris,
Have you also dismantled the jet block from the carb body? There is a very small hole for low idle mixture in the jet block and in the carb body and the engine will not idle if it is clogged.
Normally it should start and run on revs if you flood the carb and give it 1/4 throttle when starting, even if the low idle is clogged.
One very common reason for hard starting on 2-stroke engine are if the crankshaft seals are cracked/worn.
A stupid last question: I assume that you have the choke lever in right position when you start the bike? Many people have been fooled by "upside down" function of the choke of DKW. It shall be in forward position during start and pulled rearward when the engine is getting warm.
Greetings!
//Frank
Have you also dismantled the jet block from the carb body? There is a very small hole for low idle mixture in the jet block and in the carb body and the engine will not idle if it is clogged.
Normally it should start and run on revs if you flood the carb and give it 1/4 throttle when starting, even if the low idle is clogged.
One very common reason for hard starting on 2-stroke engine are if the crankshaft seals are cracked/worn.
A stupid last question: I assume that you have the choke lever in right position when you start the bike? Many people have been fooled by "upside down" function of the choke of DKW. It shall be in forward position during start and pulled rearward when the engine is getting warm.
Greetings!
//Frank
-
thunderbolt
- Tool Cleaner
- Posts: 52
- Joined: Fri Aug 14, 2015 2:49 pm
- Location: England
Re: 350NZ carburetor issues?
Hi chaps,
Last weekend I ran my boat on a lake (1961 Fairey Cinderella with a '79 Merc 500 outboard). Talking with my boating chums I realise I've made a stupid school-boy error with my DKW!
To try and start my bike I just used the fuel I had in the garage - albeit fresh fuel it was 5 litres of my outboard motor mix - therefore 50:1 made with a modern 2 stroke oil.
Of course our old bike engines were designed for a 'heavy' oil 25:1 mix, I guess a straight 40W or something similar, the oil being part of the crankcase sealing process. This is probably why I'm not getting any fuel into the engine as without the heavy oil there is no crankcase pressure, hence no induction!
I've not made a new fuel mix yet to try my theory, what oil do you guys use for your fuel mix?
cheers,
Chris
Last weekend I ran my boat on a lake (1961 Fairey Cinderella with a '79 Merc 500 outboard). Talking with my boating chums I realise I've made a stupid school-boy error with my DKW!
To try and start my bike I just used the fuel I had in the garage - albeit fresh fuel it was 5 litres of my outboard motor mix - therefore 50:1 made with a modern 2 stroke oil.
Of course our old bike engines were designed for a 'heavy' oil 25:1 mix, I guess a straight 40W or something similar, the oil being part of the crankcase sealing process. This is probably why I'm not getting any fuel into the engine as without the heavy oil there is no crankcase pressure, hence no induction!
I've not made a new fuel mix yet to try my theory, what oil do you guys use for your fuel mix?
cheers,
Chris
Re: 350NZ carburetor issues?
Hi Chris,
Back when those bikes were new there were no two-stroke oils, so they just used motor oil, Sae 30 or Sae 40.
The oil mixture has nothing to do with the crankshaft seals, they are of modern type rubber lip seals, so the oil just lubricate them, its not a part of the sealing. So if they are ok, the bike should start properly with any mixture.
Normally the most critical point in old two-strokers, if using to lean gas/oil mixture is the conrod small end bronze bushing that will seize, or worn out very fast.
Normally any two-stroke mixture oil should work ok. There are for sure different opinions about make of oil and mixing ratios.
Myself I use normal mineral two stroke oil with 4% mixture.
I know that some people use 3%, or even 2% with modern oils to get less smoke, but I want the bearings and bushings to get enough oil and the smoke does not bother me, its a part of these bikes
Greetings!
//Frank
Back when those bikes were new there were no two-stroke oils, so they just used motor oil, Sae 30 or Sae 40.
The oil mixture has nothing to do with the crankshaft seals, they are of modern type rubber lip seals, so the oil just lubricate them, its not a part of the sealing. So if they are ok, the bike should start properly with any mixture.
Normally the most critical point in old two-strokers, if using to lean gas/oil mixture is the conrod small end bronze bushing that will seize, or worn out very fast.
Normally any two-stroke mixture oil should work ok. There are for sure different opinions about make of oil and mixing ratios.
Myself I use normal mineral two stroke oil with 4% mixture.
I know that some people use 3%, or even 2% with modern oils to get less smoke, but I want the bearings and bushings to get enough oil and the smoke does not bother me, its a part of these bikes
Greetings!
//Frank