MS460 & MS260 carb tuning

[blazer]

I was thinking about a coment a while ago, where somebody said, he has known motorcross mechanics damage some chainsaws including a MS880.

 

All I can assume is a bike mechanic will tune for best free revving power. I admit I'm a bit like that, so am a bit worried I may have it wrong as I have no mfg info to work from:confused1:

 

Pls correct me if I'm wrong but I tune a saw by the normal setting air screws to std setting, warm up saw - adjust the L screw for best running, then adjust tickover. To set the H screw I rev the saw and adjust for best free revving and back it slightly just before it 4 -strokes. I have no tacho but had no probs for 10yrs using this method.

 

I tried to do some searches but no luck

[Cut4fun]

For hard working saws I tune H to 4 stroke out of cut but once in the cut the saw clears up and sounds like a mad hornet.

L I adjust till I have good throttle response from off to full throttle is crisp and fast pick up.

 

Now cookie cutting tune is totally different for short fast cuts when being timed or wanting to show off.

[spudulike]

I was thinking about a coment a while ago, where somebody said, he has known motorcross mechanics damage some chainsaws including a MS880.

 

All I can assume is a bike mechanic will tune for best free revving power. I admit I'm a bit like that, so am a bit worried I may have it wrong as I have no mfg info to work from:confused1:

 

Pls correct me if I'm wrong but I tune a saw by the normal setting air screws to std setting, warm up saw - adjust the L screw for best running, then adjust tickover. To set the H screw I rev the saw and adjust for best free revving and back it slightly just before it 4 -strokes. I have no tacho but had no probs for 10yrs using this method.

 

I tried to do some searches but no luck

 

The H screw should not be adjusted for best free running, by ear start with the saw running rich and turn the H screw clockwise until the engine revvs freely and then counterclockwise until it just "flubbs" or "warbles" a little - this "fourstroking" will stop when cutting as the saw will need more power and fuel to cut so it won't four stroke in the wood.

 

The theory is the richness in the H setting causes the engine to miss every other stroke thus sounding like a fourstroke - it is a bit like a fuel controlled rev limiter. I am guessing motocross bikes are possibly tuned in a different way but this is the mechanics of the chainsaw.

[blazer]

Thanks very much - hopefully this will help others. I don't think I'm that far out but I will give them all a retune on Sunday and let you know if they are much different. I was going to try a 2 - man set up with me adjusting the H screw under load with my son operating but this sounds much easier. I do the normal plug colour under load bit.

 

Had a prob tuning my MS280 back in the summer but it turned out to be a ign unit prob.

Edited October 27, 2011 by blazer

[spudulike]

Thanks very much - hopefully this will help others. I don't think I'm that far out but I will give them all a retune on Sunday and let you know if they are much different. I was going to try a 2 - man set up with me adjusting the H screw under load with my son operating but this sounds much easier. I do the normal plug colour under load bit.

 

Had a prob tuning my MS280 back in the summer but it turned out to be a ign unit prob.

 

It is a good idea to get someone else to operate the saw - some I videoed before I had a tach sounded fine when tuning but a bit rich on watching the vid!

 

Good luck - better to be a bit rich than lean!......in terms of £££ as well:thumbup:

[Ironbark]

Blazer, i have Stihls MS460 carb tuning guide in a PDF document thing. If you want a copy send me a PM with your email address I'll send it to you.

[blazer]

Many thanks for you help, from reading up I will need to buy a 'tacho' in the near future to ensure I get it right - any tacho recomendations at a reasonable price & where to buy one from for new & older saws.

 

When I mentioned putting a tacho on my saws, my son thought I wanted to 'pimp it up' - with,"how about fitting a sub-system and some fluffy dice":blushing:

[spudulike]

Many thanks for you help, from reading up I will need to buy a 'tacho' in the near future to ensure I get it right - any tacho recomendations at a reasonable price & where to buy one from for new & older saws.

 

When I mentioned putting a tacho on my saws, my son thought I wanted to 'pimp it up' - with,"how about fitting a sub-system and some fluffy dice":blushing:

 

Some of the yanks leave them on all the time - more the tuned and ported ones rather than workhorses - that way you can get the revvs in the cut!

 

You will need one capable of reading up to 20K rpm and a refresh of 0.5 seconds.