Jeff, not a chance in hell of pulling it over with the decomp plugged off Gadge, I could put a full crank one on it but I want to hang onto as many of those as I can, never know when I will need those. I wiped the decomp down with metho before I put the JB Weld on but it just blew it off easily, no real attempt to hold.
Norm, I'd clean the metal with Acetone, and then let the JB Weld set up for a few days - it takes that long to set up fully hard and reach maximum bond strength, IME.
Cheers, Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."
Jeff, just tried a F/C decomp and the kickback is the same. What I was thinking with the decopms that can be pulled apart it would be easier to plug the holes from the inside. I tried to rivet a plate on the back of one with JB Weld under it but now the decomp won't close. I was very careful to just go through with the drill. I have done another one and just put a patch over the 2 holes and glued them on with Araldite. See if that holds tomorrow
Gadge, the problem with blanking the 2 holes off is that while the valve is still open you get compression pressure up under the diaphragm. With a bit of luck the Araldite might hold
Hi Max, I gave them a thought a few days but I think they are probably 10mm and I would have had to make up a bush, but if it would solve it it would be worth it.
How does that work? Must have to push the knob after pulling the cord. Is there time and the valve would have to be very close to hand.
Another idea is they only kick back because they fire backwards.
. They will not fire if the ignition is off. Try a pull with ignition off then switch on when turning properly.
Probably not a workable solution There would be a way of getting DC out of the primary coil windings. Have to be the older style magneto with the separate module.and would need some clever electronics to operate an electrical valve.
Another idea that will not work.
Persevere with the decompressor valve I think Norm.
Jeff, the decomp valve with 2 holes covered solves the problem, I just have to work out what will hold on to the block the holes. This is not a problem caused by ignition firing early, it is a compression issue that must be compounded by the belt driven blade carrier. Got me stumped why but this is what it is. I can't believe these machines have been around for years and nobody has come here asking about it. The bloke who dropped it off got a full crank one from me some time ago admitted this one has been a pig of a machine, but it belongs to his father
Hi billyj It is possible but the holes are about 1/4 inch so it would need a piece of sheetmetal on the inside and also on the outside and I'm not sure how it would work on the inside. I will see how the araldite holds up tomorrow
very interesting topic. i had always thought my 24 just had higher compression ? now i know why its a bugger to pull start. i hope you sort it NormK. thanks for sharing.have you tried starting it without the belt? i am guessing yes. if a normal blade disc spins up quickly when pulled. maybe the belt is slowing the spin up and giving the decompressor enough time to fully close before the next stroke.making it hard to pull cos its closing too soon. seems it would be the opposite of this in theory, BUT ? anyway hope you fix it for us all .cheers mate.
If my collection is complete ( then how come i keep buying stuff ? ) 🤔🤔🤔🤔🤔
I don't think they are firing early just backwards which has disastrous consequences if the starter is still engaged.
This has been reported on this forum before even one which wrecked the starter. All thought it was a loose belt even the OP who thought that tightening the belt fixed the problem. I have the belt pretty tight like a guitar string but it still happens but it's not that bad. Really only when flooded.
So the chain saw decompressors are automatic and close only when the motor fires. I have never had a chainsaw like that but all mine have been from the cheaper end of the market.
In that case that would probably work on a 24. Maybe make up an adaptor from the bottom end of an old spark plug. There must still be enough compression for the motor to fire but not a lot is needed.
Yes the chainsaw decompressors close automatically when the motor fires but you have to manually open the decompressor before starting, an adaptor would be easily made.
The decom valve I blocked 2 holes off didn't solve the problem today, it reduced the kickback to being not too bad. I ended up fitting another decomp valve which had the brass piece in the end of it and that removed all the kicking back. Motor still takes a few pulls to get it started but the owners doesn't want the carby modified so that is his problem. I might fit a modified one just to prove to me that it will solve this problem and then put his original one back.
I like the idea of restricting the vacuum supply to the decompressor better than trying to restrict air flow to the other side of the diaphram which gets mixed up with the compression gases. Are you sure its nothing to do with being slightly flooded? Thats the only time that it happens with mine usually when trying to blow out the system so that it will start. It usually will do nothing for a couple of pulls then kickback once or twice then start. Its not very often only when too enthusiastic with the primer bulb.Most of the time it starts pretty well but a heavier pull is needed compared to a ordinary PT. This one still has a basically unmodified carby too, just the kill switch disconnected. It was working OK so " If it ain't broke don't fix it" I have sent a modified carby with it but there has been no need to fit it.
I have never taken much notice of these decompressors. Always OK and left alone. the restrictor is in the end where the tube goes on I suppose.
I like the idea of restricting the vacuum supply to the decompressor better than trying to restrict air flow to the other side of the diaphram which gets mixed up with the compression gases.
Yep, +1 on that.
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I have never taken much notice of these decompressors. Always OK and left alone. the restrictor is in the end where the tube goes on I suppose.
There's a pic of the later type black decomp nozzle, with the restrictor, over in my decompressor rebuild thread [see the 'stickies' at the top of this forum section]. Dunno about other sources, but the ODK shop has these in stock; link is in the first post of that thread.
Cheers, Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."
