6.75 Briggs not starting...Easily

[Pet982]

Those valve clearances are good, as I posted earlier you have a lean running condition, which involves the carb. I'll bet the float level is set to low, that is why I suggested rebuilding the carb. Yes I know it is new, but just last week I had a brand new one leak like a sieve, you can get a bad one at times.

Even though when I get it running it will run perfectly? Just to get it run I have to pour gas down the throat of the carb.


I bought a HFT leakdown tester. Could compression be a factor? If not... whats the harm of another tool in the tool chest?

 

[Pet982]

I proformed a leak-down test and that seemed to have checked out. The gage was a little touchy but the cold engine seemed to have 20% leakage (buy the rings, the muffler and carb was quiet.)


I contacted where I bought the new carb from to see about another one. But something tells me I am missing something mechanical in the engine as, if the repair place was truthful. They claimed they put a new carb on it also so that would make 3 carbs so far.

 

[Rivets]

The carb is set too lean for starting, that is why you need to pour in extra fuel. Three things will cause this. 1. An air leak at one of three places. O-ring between carb and manifold, cracked manifold, gasket between manifold and block. 2. Auto-choke not operating properly to close the air horn during starting. 3. Fuel in the float bowl not at the proper height, causing the need for a higher than normal vacuum needed to draw the fuel into the cylinder.

 

[Pet982]

Another new carb came in today and I installed it. Its still doing the same thing.



The new carbs are a primer type and when I push the primer, a squirt of gas squirts up the main jet. When I pull the cord itsometimes sputters for 5-10 sec. but never gets up to full RPM. I can put it 10+ times in a row with no sputtering, when I check the plug it does have gas on it but not soaked

 

[mechanic mark]

https://www.briggsandstratton.com/n...nemanuals.html?searchrequested=126t02-0675-b2

adjusting valves correctly is very important, you have to be on correct stroke, both valves closed & rocker arms loose, 1/4" past TDC on B&S engines, you can remove spark plug & rotate engine by hand on top screen above flywheel, gently place a screwdriver in spark plug hole to let you know when piston is at TDC, if rocker arms are tight & valve is open rotate engine 180 degrees & check for rocker arms loose to TDC then 1/4" past & adjust valves.

 

[pugaltitude]

Can I ask why its now a primer instead of auto choke?
If I remember right both systems use a different coil which might cause your problem.
Also cylinder head will be different.
Also have you checked the flywheel key as it could be sheared and timing may be out?

 

[Pet982]

Can I ask why its now a primer instead of auto choke?
If I remember right both systems use a different coil which might cause your problem.
Also cylinder head will be different.
Also have you checked the flywheel key as it could be sheared and timing may be out?

I check the key it was slightly off but the key looked all in tact. when I put it back all lined up and it still would not run.

When I first started messing around with it and got it to run when priming it I decided to try a new primer carb on it. When I looked up the parts for the model / s numbers a P/N was listed to both types of carbs so I decided to give the primer carb shot. The air filter had the bulb spot plugged and I added the bulb.

All other parts appear to have the same numbers correct me if I'm wrong that's why I'm hear to learn things. How are/ why would the heads different? Air Flow?

The valve clearances measured within spec when putting the piston 1/2 way down the power stroke(combustion).

 

[BlazNT]

If the key is even 1/2 a mm off then timing is off. Replace the key if it is not perfectly square.

 

[pugaltitude]

I check the key it was slightly off but the key looked all in tact. when I put it back all lined up and it still would not run.

When I first started messing around with it and got it to run when priming it I decided to try a new primer carb on it. When I looked up the parts for the model / s numbers a P/N was listed to both types of carbs so I decided to give the primer carb shot. The air filter had the bulb spot plugged and I added the bulb.

All other parts appear to have the same numbers correct me if I'm wrong that's why I'm hear to learn things. How are/ why would the heads different? Air Flow?

The valve clearances measured within spec when putting the piston 1/2 way down the power stroke(combustion).

So your problem could be the air filter back plate.
If it is autochoke, where the gasket fits will be flat.

On a primer back plate where the gasket fits it has a channel for the air to go when the primer gets pushed.

Could it be this?

 

[Pet982]

So your problem could be the air filter back plate.
If it is autochoke, where the gasket fits will be flat.

On a primer back plate where the gasket fits it has a channel for the air to go when the primer gets pushed.

Could it be this?

No the backing plate does have the horseshoe channel. All I had to do was take the plug out and put in the bulb. When I push the primer a squirt of gas does shoot up the main jet.

Could the compression release system be screwed up?