tuning a saw?

[billpierce]

i don't know what the hell is going on now! feel like a right moron!

 

so base settings for the ms 361 on the side read H 3/4 out, L 1/4 out. this will run but seems to be screaming a bit at high revs. 2 things are bothering me. the L doesn't make any difference at all when you wind it in or right out i.e. you don't notice chain starting to move when you lean it etc or the saw dying. is this an issue? i can't see any caps on it

 

the saw seems to be on the weak side in the cut the rpm on the tach foes all over the shop when you get to 9200k so as i understood it i should just leave it there as the limiter is interferring? it feels to my ear that it wants leaning out but i obviously don;t want to damage anything. also with the carb this rich its hard t get it to idle even with idle screw in, the L does have an effect but still hard to get it to tick over reet nice.

 

on the plus side changed a carb on a ms170 and tuned it up with success!

 

again really really appreciating all the help!

[billpierce]

also what is most important - chocolately spark plug or tach telling you your H is tuned a bit lower than the max RPM? also noticed the the throttle butterfly on the ms361 carb was only opening 1/4 - the throttle wire looked a little bend so straightened that up but same problem as above.

[spudulike]

Right - STOP - the markings on the side of the saw are with the LIMITERS in place, you have probably got the limiters removed, it is no wonder the saw is screaming like this - it will be running VERY lean.

 

Take a look at the screws with a torch and if you can see a red and a white plastic cap on the H & L screws they are limited but if they are typical slotted screw heads, they have been removed and using one turn out on each as a starting point will be best.

 

I have seen an MS880 killed in the way you have adjusted the carb!!!

[billpierce]

thanks spud

 

got there eventually all is pretty good but it took me literally hours of minor adjustment (1/8th of a turn or less) to get to to even tick over. even then it feels really wierd compared to the 034 av super i just tuned (seems to run great and took 5 mins with the tach.

 

on the ms361;

 

the L screw seems to have no noticable effect i.e if you lean it the chain won't move, engine doesn't pick up, doesn't cut out.

 

same with the idle, you might gain 400rpm with it right in and it'll cut out with it out. i've taken the carb to bits and looks clean and ok. and everything appears to make good contact (idle screw with throttle lever etc.)

 

is there something wrong or is it just really different to my 660, 200t, 020t, 170, and 034?

 

AND last question (have only found people argueing about this on the net.) I have tuned to roughly 1000rpm below max rpm as this sounded like quite enough for the saws (with bar and chain on at correct tension but not in the wood.) is that definatley ok for the saws or should i be keeping a close eye on spark plug colour?

 

your help is invaluable, if your ever in northumberland the pints are on me!

[spudulike]

thanks spud

 

got there eventually all is pretty good but it took me literally hours of minor adjustment (1/8th of a turn or less) to get to to even tick over. even then it feels really wierd compared to the 034 av super i just tuned (seems to run great and took 5 mins with the tach.

 

on the ms361;

 

the L screw seems to have no noticable effect i.e if you lean it the chain won't move, engine doesn't pick up, doesn't cut out.

 

same with the idle, you might gain 400rpm with it right in and it'll cut out with it out. i've taken the carb to bits and looks clean and ok. and everything appears to make good contact (idle screw with throttle lever etc.)

 

is there something wrong or is it just really different to my 660, 200t, 020t, 170, and 034?

 

AND last question (have only found people argueing about this on the net.) I have tuned to roughly 1000rpm below max rpm as this sounded like quite enough for the saws (with bar and chain on at correct tension but not in the wood.) is that definatley ok for the saws or should i be keeping a close eye on spark plug colour?

 

your help is invaluable, if your ever in northumberland the pints are on me!

 

Most carbs tune up in a very similar way and if the L screw is making no difference then I suspect a fault. The theory is that if the screw is turned all the way in, the engine will die as it is getting no fuel. If it continues to run, I would suspect a leaking welch plug allowing fuel to be picked up through the leak rather than via the normal route - past the L screw.

 

One thing I have found on some saws that have been messes around with - the idle screw is turned well in and the L screw is well out of position so would personally take the limiters off and turn the screws all the way in then both out one turn and then lower the idle until the idle is around right and then re adjust the L screw to make sure it is OK.

 

I usually use a tach to adjust the carb and that is on a saw that has been checked over - fuel system OK, the throttle is being held open to its maximum opening, breathers etc

 

You can check the plug colour and it gives an excellent indication things are correct but the tach does do this in a much shorter time - I can't cut a cubic ton and then do a plug chop on each saw - the tach as well as the factory settings give a nice clean easy way to set a saw up and will be used by any decent tech. If the tach is used correctly, the plug colour should be OK. The method you have adopted is fine!

 

Custom tuned saws are a different beast and to go by the sound/plug colour is common but would still use a tach to bench mark a saw - I usually set a tuned saw up to maximum revs or a few Krpm over if it is heavily fourstroking still.

[billpierce]

Thanks, man!

 

Pleased it sounds like its not just me being a special. I will go check these welch plugs now. also when you say limiters do you refer to the blue and red plastic bits that have been removed or do you mean the wee springs behind the screw heads? i guess your talking about bits of plastic? I have used the all in then one out which will just about get it to idle only at 2100-2400 and sitting the LA screw in won't effect this.

 

also when you say " the tach as well as the factory settings give a nice clean easy way to set a saw up and will be used by any decent tech." do you mean factory settings starting at one turn out and tweeking from their and knowing the max rpm?

 

so with plug colour i will only really be able to tell after a good hours use or something? whats all this chatter about killing the saw in the cut to check all about then?

 

 

seriously now, thanks alot

[lakeyboy]

Killing the saw in the cut is I suppose similar to plug chop I was told to do on my yamaha dtr 125 im guessing its to do with fuel being burnt under load, maybe someone else will have a better explanation than me

[spudulike]

Thanks, man!

 

Pleased it sounds like its not just me being a special. I will go check these welch plugs now. also when you say limiters do you refer to the blue and red plastic bits that have been removed or do you mean the wee springs behind the screw heads? i guess your talking about bits of plastic? I have used the all in then one out which will just about get it to idle only at 2100-2400 and sitting the LA screw in won't effect this.

 

also when you say " the tach as well as the factory settings give a nice clean easy way to set a saw up and will be used by any decent tech." do you mean factory settings starting at one turn out and tweeking from their and knowing the max rpm?

 

so with plug colour i will only really be able to tell after a good hours use or something? whats all this chatter about killing the saw in the cut to check all about then?

 

 

seriously now, thanks alot

 

The limiters are the coloured plastic caps and Not the springs.

 

The factory settings are used to start, you then adjist the idle and L screw and then tach to achieve the correct max revs!

 

The plug colour -after 15-30 mins, the plug will colour up and should achieve a nice coffee brown colour - it is best to do some long cuts before you stop the machine - you will get by without pulling the plug after stopping the saw mid cut - still remember holding the old 400/4 flat out before killing the engine and pulling in the clutch - around 100mph I think - on private land of course:001_rolleyes:

[spudulike]

Thanks, man!

 

Pleased it sounds like its not just me being a special.

 

Bill - you are special to all of us on Arbtalk:lol:

[billpierce]

Bill - you are special to all of us on Arbtalk:lol:

 

feeling the special love!

 

 

 

took carb to bits, all looks good welch plugs look snug as ought but expect i can't tell with the aye. put it all back together saw def still runs with L right in.

 

so cheap chinese carb time? £35 quid delivered

 

or NEW stihl one £113 inc vat with L and S

 

or i fix it some how? feels like a carb kit ain't going to change much as diaphram looks good etc? or i send it to someone for fixing?

 

as ever, thanking you