Ronie's 660 kit saw

[MustangMike]

I have sometimes had carb tuning problems that made me think I had an air leak.

 

[Ronie]

It had a leak at the carb boot, I replaced the OEM boot ring with an aftermarket one and that seal it and stopped the RPM from jumping up after a second and it runs better. It still has the burble after the cut and srcarr52 suggested that it could be the pop off, I'll increase it and see if that helps. Here's how it's doing now, It's to hot right now so it's just tuned it by ear.

 

[Maintenance Chief]

That burble is concerning?

 

[Ronie]

That burble is concerning?

I don't know, it just bugs me. lol

 

[Nutball]

Maybe the cylinder is getting too hot because FT and Hyway and other chinese cylinders often have poor air flow because the fins are super thick at the casting seams.

 

[Ronie]

Maybe the cylinder is getting too hot because FT and Hyway and other chinese cylinders often have poor air flow because the fins are super thick at the casting seams.

It was like srcarr52 said, I increased the pop of pressure and the burbling after the cut went away.

 

[Nutball]

That's good. I wonder what the science is behind that change and how it affects that burble. I may be way off, but it sounded to me like it was getting too little fuel when spooling down, like there's an air leak in the main nozzle check valve, or it was too hot. Was it getting too much fuel instead? I don't know much about internal carb adjustments.

 

[Ronie]

That's good. I wonder what the science is behind that change and how it affects that burble. I may be way off, but it sounded to me like it was getting too little fuel when spooling down, like there's an air leak in the main nozzle check valve, or it was too hot. Was it getting too much fuel instead? I don't know much about internal carb adjustments.

With I could help you with the why but I have no Idea.

 

[MustangMike]

The weaker spring allows addl fuel to go through.

 

[huskihl]

He actually raised the pop off pressure. Which would require the screws to be tuned richer. Has to be something to do with the screw position.

 

[srcarr52]

That's good. I wonder what the science is behind that change and how it affects that burble. I may be way off, but it sounded to me like it was getting too little fuel when spooling down, like there's an air leak in the main nozzle check valve, or it was too hot. Was it getting too much fuel instead? I don't know much about internal carb adjustments.

It's actually dumping fuel on the decel because the needle/seat can't hold the fuel back from the vacuum (demand) of the engine, which causes an abrupt decline in RPM followed by a short acceleration period when the puddled fuel burns off to the lean "racing" mixture, and the cycle repeats till idle RPM is achieved.

 

[Jason628]

I had an issue with one of the boots not sealing when I checked it with vacuum swapped with another aftermarket one and it sealed up.

 

[Jason628]

Another pic

View attachment 304992

That probably came off of your table

 

[Ronie]

I wasn't real happy with the torque of the Hyway cylinder so I decided to try a big bore cylinder and see what it's like. It's just a cheap white box cylinder but it doesn't look to bad. I'll put up the timing numbers once I get the saw apart and the wheel on it.

View attachment 305862

 

[Maintenance Chief]

View attachment 305864 View attachment 305865 View attachment 305859 View attachment 305860 View attachment 305861 I wasn't real happy with the torque of the Hyway cylinder so I decided to try a big bore cylinder and see what it's like. It's just a cheap white box cylinder but it doesn't look to bad. I'll put up the timing numbers once I get the saw apart and the wheel on it.

View attachment 305859 View attachment 305860 View attachment 305861 View attachment 305862

I guess you won't have any free port issues.

 

[Ronie]

I guess you won't have any free port issues.

It might, I thought all the 660 big bore cylinders had free port issues.

 

[Ronie]

I guess you won't have any free port issues.

I see what you mean, because the piston is in the cylinder in the pic at 0 squish and it's not free porting.

 

[Ronie]

I guess you won't have any free port issues.

I took a closer look at it and it's going to free port a little.

 

[Maintenance Chief]

I find alot of misinformation about aftermarket parts , but the problem is compounded by the fact that some of the parts with issues are still out there . Like the 660 carb I bought last year had the same problem that was discovered 3 years ago, but newer or recently manufactured products are usually recast or fixed.
The blue 660 my friend bought had zero problems that were discussed 2 years ago.

 

[Maintenance Chief]

If the parts you buy have been sitting in a warehouse for a few years they'll be just like that.