# setting high jet on saw



## scrench (Dec 8, 2004)

should the high be set on with the bar on ? or can it be set with the bar off ? the reason i ask is i just done a piston and cyl on a 066 and the customer has a 16 an 18 and a 24 inch bar the 16 and 18 are 3-8 chain and the 24 is 404 was just wondering if it might be leaning out too far on top end with the 16 and 18 or will it make a difference ? can i set it with the tach with no bar on it ?


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## hankster (Jan 1, 1998)

Yes, the carb on the saw HAS to be set with the chain on. Running a saw at full throttle with no chain severly over reves the engine. I would set it with the smallest bar and it should be fine for the larger bar.

I personally don't use a tach to adjust a carb... best bet is to go by sound, how well it accelerates, etc. But that does take some practice.

As an additional note: Any handheld 2-cycle engine should only be tuned with the accessories attached. If it's a weekwacker, make sure you have the correct string with the proper length. If it's a blower, make sure the tube is attached... etc.


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## scrench (Dec 8, 2004)

set it with the smallest bar , thats what i was thinking i dont use a tach on push mowers or tillers or trimmers but i use it on every saw i work on ,,,,,,, thanks


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## t_andersen (Mar 13, 2005)

*Which tach?*

Is it ok to use a normal car engine tachometer?


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## bbnissan (Nov 7, 2004)

> Is it ok to use a normal car engine tachometer?


Generally speaking...no (although the tach for an outboard boat motor may work). The problem is the fact that the 4 cycle engine and 2 cycle engines fire differently.

You can, however, find an inductive pickup tachometer at a autoparts store that will work. I have a tach like this that I got in an engine analyzer kit several years ago at Pep Boys. The tach has a selector switch on it to choose between 2 cycle and 4 cycle.


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## scrench (Dec 8, 2004)

i havent seen a tach for automotive that would go that high , the tach i use will self adjust for 2 cycle or four cycle of course its the best in the world STIHL <-----((((((((( ...........


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## scrench (Dec 8, 2004)

bbnissan said:


> Generally speaking...no (although the tach for an outboard boat motor may work). The problem is the fact that the 4 cycle engine and 2 cycle engines fire differently.
> 
> You can, however, find an inductive pickup tachometer at a autoparts store that will work. I have a tach like this that I got in an engine analyzer kit several years ago at Pep Boys. The tach has a selector switch on it to choose between 2 cycle and 4 cycle.


 
are you sure that switch isnt for like 2 cylenders or 4 or 6 or 8 cylenders ?


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## hankster (Jan 1, 1998)

2-cycle or 4-cycle, it doesn't matter. The plug fires on every revolution. Remember, the plug fires off the flywheel and not via a distributor like a car engine.



scrench said:


> set it with the smallest bar , thats what i was thinking i dont use a tach on push mowers or tillers or trimmers but i use it on every saw i work on ,,,,,,, thanks


 That's funny, I use a tach on 4-cycles and not 2-cycles... guess it's whatever you are used to.


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## scrench (Dec 8, 2004)

2-cycle or 4-cycle, it doesn't matter. the instructions that came with my tach said it does ? wouldnt a two stroke fire twice as much ? or twice as fast ?


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## hankster (Jan 1, 1998)

Not on a small engine. The plugs fires off the mag located on the flywheel. Since the flywheel is connected to the crank it turns at the same speed as the crank. There is no circuit in a small engine to make the plug fire every other revolution so the plug does fire on the exhaust stroke on a 4-cycle small engine.

On a large engine that has a distributor, the distributor turns at 1/2 the speed of the crank so you only get spark on the compression stroke.

Turn your engine over by hand and you will see that the mag is fired every revolution... or better yet, tell me what makes it NOT fire on the exhaust stroke?


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## scrench (Dec 8, 2004)

not saying it dont fire on the exaust , but am saying that my tach has a setting for four cycle and 2 cycle , maby it has something to do with 3600 rpm verses 13000 rpms my tach actually has a setting for 2 cycle then four cycle 1, 2 ,3 , four cyl...


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## hankster (Jan 1, 1998)

If it has a 4-cycle setting then it most likely would be used with an engine that uses a distributor.


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