Rebuild K760 Carb or not

[angellonewolf]

This is the most bizarre thing. I fitted a new ignition coil wire and tested the kill switch. Still doing the same thing. Have to put pressure on the top for it to run.

Maybe intake rubber tubes is what I am thinking now. The ones on it are supple and I do not see any cracks when squeezing etc but clearly something is still wrong with it. So I'll order yet more parts and try for about the 8th time to fix this saw.

I did go ahead and buy another Stihl con saw at this stage so I can get some forking work done instead of working on the darn saw. As soon as the husky is running OK I will be selling it & keep the Stihl.

If anyone has any ideas on the current issue I am all ears.

to rule out the electrics side remove the wire off the coil this will test if any of the electrics switches cables are faulty as all it does is earth the coil if there is any wires that are rubbing and worn the insoluation through or the on off switch is dodgy

just remember they only way to turn it off when you done this the only way to stop it would be to turn the choke on to flood it

 

[Kram]

Maybe intake rubber tubes is what I am thinking now. The ones on it are supple and I do not see any cracks when squeezing etc but clearly something is still wrong with it

Spray brake cleaner while its running and look for change of revs

 

[JOEPRO]

to rule out the electrics side remove the wire off the coil this will test if any of the electrics switches cables are faulty as all it does is earth the coil if there is any wires that are rubbing and worn the insoluation through or the on off switch is dodgy

just remember they only way to turn it off when you done this the only way to stop it would be to turn the choke on to flood it

Spray brake cleaner while its running and look for change of revs

Thanks for the replies I will take a look at those items tomorrow.

This is the Stihl Saw I bought good used will be here next week:

It's a really clean one and fully serviced.

 

[angellonewolf]

Thanks for the replies I will take a look at those items tomorrow.

This is the Stihl Saw I bought good used will be here next week:

It's a really clean one and fully serviced.

View attachment 440159View attachment 440160View attachment 440161View attachment 440162View attachment 440163

looks clean

 

[8ob]

On all of these small saws/two strokes you are far better off spending ten minutes with a vac tester/bungs than relentlessly changing parts to try and make it run.

Bob

 

[JOEPRO]

On all of these small saws/two strokes you are far better off spending ten minutes with a vac tester/bungs than relentlessly changing parts to try and make it run.

Bob

Amy suggestions on where I may find a set of suitable test bungs for a K760 please.

I don't work at small engines so I don't have any of this stuff.

 

[8ob]

Amy suggestions on where I may find a set of suitable test bungs for a K760 please.

I don't work at small engines so I don't have any of this stuff.

If its a round port I use the stepped plumbers pipe bungs, if its flanged/bolted I make up plates.

 

[JOEPRO]

OK I think I may have figured out this last problem. Its not electrical I am sure of it, nothing changes when pressed down I had a multimeter on it earlier.

I completely dismantled the rubber intake pipes and twisted then every which way - no cracks.



The issue I think is idle throttle adjustment. Not mixture but blade adjustment which must have came set too low on the new carb!

See how the carb is mounted VS the throttle linkage:



Pushing down on the housing must have been just very slightly pressing against the throttle.

There is no way of accessing this idle blade adjustment without removing the carb so tomorrow I'll try it a 1/4 turn advanced at a time and see does this finally make it run correctly.

Old spare carb but see the flathead:



I was adjusting the low jet screw on bottom which is accessible when installed but didn't realise the other adjustment is there or expect it to come set to "off" on a new genuine Husqvarna carb.

 

[JOEPRO]

So that's this one concluded. It was the idle speed on new Husqvarna carb set to shut out of the box. Turned up now and it can idle properly with the blade not turning at all.

I learned a few things here when taking on this 2 stroke repair of mine. Do NOT bother with ebay China carbs or rebuild kits. Genuine parts only in that regard to ensure success. Check the compression etc at the beginning too so you know the full condition up front.

I will await the Stihl turning up and will run both saws next weekend and see how they compare. I bought the Stihl for £180, I could sell it for £280 locally so either way this will work out fine when I make a final decision which one is to go.

 

[JOEPRO]

I dont think the Husky project will ever end

The new cylinder kit is giving 100psi which is below the min of 120. As a comparison my used Stihl saws are reading near 150psi and they are on the original cylinders.



I have the Rockauto cylinder here too which does look to be from a different factory and possibly higher quality. I will time how long it takes me now to swap out the cylinder....

 

[JOEPRO]

The old new cylinder was scored inside. It was assembled with plenty of oil and engine assembly lube in a clean environment. Not ran hard at all only ran for 10 mins. Pure junk



New piston (again) going in



And all done in about 40 mins. Didn't have to remove carb either as per pic.

It certainly feels alot harder to pull over now suggesting the compression should be up. I ran it for 5 mins or so inside my garage as its Sunday and all doors open now to vent the smoke!

 

[JOEPRO]

Too much clearance causing excessive piston slap?

Either that or the cylinder wall is out of round / poorly machined.

In any case, the second cylinder gives the same just under 100psi. So that must be the norm for the aftermarket stuff. Or there is a bed in period(?) Not sure.

 

[angellonewolf]

waiting to see if the new bore and piston make a differance ive one to do and got a cheapy kit but held off doing it at mo

 

[CatastrophicFailure]

Partner K650s used to have a problem with crank seals. or I had a problem picking secondhand K650s, You see this most clearly on high-mileage hedge trimmers. They start, idle but die when you point them at a hedge. The seals have worn grooves in the crank. The trimmers won't run in the position they have been most used. Make what you will of this theory but if you want it backwardsish, I put a 2hp outboard together with a tiny pitted bit on the crank where the seal ran. It ran fine for a little while till it wore the seal down... Make what you will...

 

[Adal]

Hello gents can anyone help me please. i have a K760 I have put a new primer bulb in and it will not prime the primer works I tried to blow through the intake on the carb but I can not can anyone help

 

[angellonewolf]

Hello gents can anyone help me please. i have a K760 I have put a new primer bulb in and it will not prime the primer works I tried to blow through the intake on the carb but I can not can anyone help

might be worth starting a new thread

but before any thing else take out spark plug half a teaspoon fuel in bore (2 stroke mix) put back in plug and put on choke and try start

it should fire/cough for half a second

if it does not then you got more problems than just carb

if it fires (might even run for a bit as the sucking of the engine might pull the fuel through)then start looking at the carb and fuel pipes (fuel pipes they split )