McCulloch BP1 runs high speed

[robrep]

I have acquired a BP1 from an old friend. I cleaned it up and got it to run, my problem is it runs too good. It won't run less then 6000+ RPMs. The throttle plate is closed all way, made new intake gaskets and installed them, checked for cracks etc. I can't figure how the thing is running like this. Would appreciate any help. Thanks Robert.

 

[wcorey]

With the throttle plate closed it pretty much has to be an air leak...

 

[jacob j.]

I'm betting it needs seals...they always do.

 

[Al Smith]

That thing has one goofy carb .I've got the drawing on micro fiche but I can't copy and post it .I'll be back home tomorrow and see if the slides have any information .

 

[Deets066]

With the throttle plate closed it pretty much has to be an air leak...

I’d agree

 

[robrep]

I'm betting it needs seals...they always do.

Kind of where my thinking was leading. Im going to have to think about this don't know if i want to overhaul the thing??? I might just sell it and let someone else have the fun of an overhaul. I have a bunch of other old chainsaws that need some attention. Thanks for the input.

 

[Steve]

@heimannm

If anyone can help its Mark.

 

[heimannm]

The throttle mechanism works indirectly on the governor shaft to pull the throttle closed. Make sure that when the saw is running the mechanisms all operate properly and can actually move the throttle. If the throttle actually closes and the saw still runs too fast then it is most likely and issue with the seals. Did you back the idle speed screw out all the way?

The small shaft with the aluminum vane attached sets in the air stream off the flywheel to push the throttle closed limiting the RPM.



I had some issues with one where the throttle actuator shaft was a bit sticky and the throttle did not open quickly when the trigger was pulled but I had not had any problems with the throttle closing.

Mark

 

[Al Smith]

I kind of got detained and didn't make it back home until today .I just looked at the micro film and it only said about the usual funky seals
The carb however is a study in itself .The call it a fuel injector for some reason .Maybe because it has a double diaphragm It has a difusser cone that at idle directs the incoming air to the lower side of the carb intake where it blows through an orifice and picks up the idle which is on the inboard side of the throttle plate .I don't know if something was wrong or the cone missing if that would do anything or not.
I've seen a grand total of two or three of these things but never one that ran .Someone tried to sell me one,Dan Henry maybe .It didn't have all the parts and I didn't feel like going on a wild goose chase to find them.

 

[robrep]

The throttle mechanism works indirectly on the governor shaft to pull the throttle closed. Make sure that when the saw is running the mechanisms all operate properly and can actually move the throttle. If the throttle actually closes and the saw still runs too fast then it is most likely and issue with the seals. Did you back the idle speed screw out all the way?

The small shaft with the aluminum vane attached sets in the air stream off the flywheel to push the throttle closed limiting the RPM.

View attachment 171904

I had some issues with one where the throttle actuator shaft was a bit sticky and the throttle did not open quickly when the trigger was pulled but I had not had any problems with the throttle closing.

Mark

The throttle plate closed all the way opens and closes smoothly. I did not try it with the deflector in maybe that has something to do with it. I do have a video of it running just don't know how to get it on for people to see. PS i am computer illiterate thanks.

 

[Al Smith]

Mark would know because I'm not certain .According to the drawings and explanations the deflector channels the air down on idle but over the whole thing on throttle up .I'll look at it again to make certain later on today .However thinking out loud if the throttle plate was completely closed there would not be enough pressure drop over the high speed out let and unless the plate had a slot there wouldn't be enough air to support the high speed .

 

[Nick140m]

Is the bp1 available for sale robrep?