Tuning advice

[Ledburyjosh]

I am checking the high end revs of my MS460 after putting a duel port exhaust on.

It's running at 14200rpm. With a 25" bar and chain on.

 

I believe it should be 13500rpm max. So needs to be brought down a bit.

 

So a couple of questions:

 

Should the H revs be set with a bar and chain on or just the engine unit?

 

Can any one confirm if the 13500 max RPM is correct?

 

And generally any tips on anything else I can do?

 

Thanks

 

[spudulike]

Maximum revs are 13500 so I would aim for around 13,000rpm as it gives a degree of safety if you get a slight air leak, slight blockage in fuel filter/gauze strainer etc.

The saw should always be set with the load of a bar and chain fitted and also with a clean air filter. Get it up to operating temp before setting.

You may need to pull out the H screw limiter cap - a wood screw will do it if it is still in - the cap is red in colour. I usually screw the wood screw in, turn it gently anticlockwise until it will go no further (this aligns the small key tab) and then pull it out, turn the H screw anti clockwise 1/2 turn and refit the cap as I don't trust people to fiddle and screw up my setting!

You then just rev the saw flat out for a couple of seconds, register the revs and adjust the H screw anti clockwise if too high. This brings in more fuel and acts like a rev limiter for the saw. 

This model and the MS361 tend to over rev when well worn in and the H caps usually need removing.

 

[Stubby]

1 hour ago, StephenMews said:

 

I am checking the high end revs of my MS460 after putting a duel port exhaust on.

It's running at 14200rpm. With a 25" bar and chain on.

 

I believe it should be 13500rpm max. So needs to be brought down a bit.

 

So a couple of questions:

 

Should the H revs be set with a bar and chain on or just the engine unit?

 

Can any one confirm if the 13500 max RPM is correct?

 

And generally any tips on anything else I can do?

 

Thanks

 

 

Bar and chain on .

[Ledburyjosh]

That's great. Very comprehensive answer, much appreciated. The tip for getting the limiters out was super useful.

The saw is back down to about 13000 rpm. Sounds much better now, doesn't seem to cut much or any slower either.

Thanks

[spudulike]

All good, no problem, strong saws and should last a long time.

[Echo]

On 16/03/2022 at 10:33, StephenMews said:

 

I am checking the high end revs of my MS460 after putting a duel port exhaust on.

It's running at 14200rpm. With a 25" bar and chain on.

 

I believe it should be 13500rpm max. So needs to be brought down a bit.

 

So a couple of questions:

 

Should the H revs be set with a bar and chain on or just the engine unit?

 

Can any one confirm if the 13500 max RPM is correct?

 

And generally any tips on anything else I can do?

 

Thanks

 

 

That is not good, slow it down, turn out the high needle, see how it runs,

if it is lively enough now on the low end with good throttle response then

you can probably leave the low screw alone, but don't run it at the current

speed, and make SURE the saw is warm before adjusting it, other ways

the tune will change when it does warm up.

[Ledburyjosh]

I'm after some more advice please.

The same saw, ms460.
I have dropped the rpm to around 13000.

I've now found the saw stalls occasionally. This happens after a cut once full throttle has been released. Or when the saw has had the chain brake on, and then released it stalls just as the throttle is touched.

Prior to dropping the RPM the saw ran and idled without issue.

Any advice on this would be great.

Is there a certain RPM is should idle at?


Thanks

[spudulike]

The L, H and LA screw really need to be adjusted together but on this saw, thankfully, the L&H screws are independent and don't impact on each other. 

You have set the H screw...fab.......if the L screw has the limiter still on it, it is probably pretty much OK but the usual method is to wind it in until the revs rise and then drop back until the saw either stalls or is close to it. You then turn the L screw anti clockwise and the revs will increase and start to fall.....as the screw is undone, the revs will go from even to slightly uneven and you may feel the saw starts to rock or judder slightly - the point this starts is bob on where it needs to be and you then adjust the idle speed to 2500 rpm - slightly faster if the saw is stalling but not so fast the chain is pulsing forward.

Stalling after a high speed run can be down to an over rich carb but if the H screw is set correctly, it is probably the Idle setting.

[Ledburyjosh]

Great thanks again. I shall go through this sequence once the saw has been running a while tomorrow.

Thanks