ms460 over reving, seals maybe? carb?

[1953greg]

guys, new problem for me.

the 460bb has began over reving when in the horizontal position. not sure how much, maybe to 15k, but it has lost its 4 cycle blubber in the horizontal. when raised to verticle it 4 cycles as usual at about 13.3k no load w/ bar n chain. up n down back and forth from 2 cycle to 4. really weird. any ideas??

thanks in advance good day 1953greg

 

[Tree Sling'r]

It could be many different things. Since you installed the BB have you checked the head bolts? Did you use a new head gasket? If not - did you use gasket sealer - was it fuel safe. Crap in your carb? even the littlest will make you saw race.
It does sound like it is sucking air.

 

[THALL10326]

guys, new problem for me.

the 460bb has began over reving when in the horizontal position. not sure how much, maybe to 15k, but it has lost its 4 cycle blubber in the horizontal. when raised to verticle it 4 cycles as usual at about 13.3k no load w/ bar n chain. up n down back and forth from 2 cycle to 4. really weird. any ideas??

thanks in advance good day 1953greg

Quick way to find out if its a seal, have it pressure/vac tested. Its really the only way to know for sure whether your seals are leaking. Those two simple tests will also locate other air leaks(if you have any) such as a leaking manifold, pulse hose, cylinder gasket and crankcase as well. Don't know if you have the guages and flanges to do the vac/pressure tests but if you don't its well worth having it checked. Thats a costly saw and a good one. If ya spend 25.00 bucks having it tested its money well spent. Once its tested the results will lead to whatever is causing your saw to lean out as you described. Without those tests your sorta in the dark as to what all is going on with that saw. Way too many possibles to guess at without getting it tested. The testing will narrow down the issues your having greatly. Get her tested and go from there. I got the older version of your 460, the 046 and if you like yours as much as I like mine get that baby tested, its a very good performing saw. Be a shame to fry it.......................

 

[1953greg]

head bolts are tight. no oil stains. i did install new head gasket. 8-10 tanks have been through it with no problems til today. the most confusing part, and probably the most telling symptom, is the verticle to horizontal 2 cycle to 4 cycle change. every time as quickly as 2 seconds from bar up to horizontal. didnt try rotating from bottom to side back n forth. just up and down.

dont own the vac/pres pump. i guess thats my next purchase. the saw can wait til. will this one work?

http://search.stores.ebay.com/MACNA...lterQ20PumpQ20wQ2fQ20PressureQ20GaugeQQsofpZ0

hey thall, this saw has your air filter flange on it! thanks again

1953greg

 

[NWCS]

check your intake boot, fuel line, impulse line and crank seals. anytime movement causes problems i suspect the rubber parts. ones like this can be a pain in the rear...

 

[Lakeside53]

It could as simple as a bad metering diaphragm in the carb or, as others have suggested, pretty much anything that flexes. It's not likely to be the crank seals as these are position independent and in any case, usually affect idle rather than the high end.

A full vac and pressure test is your best option to rule out (or in) a leak. If you're doing this yourself, the pump you linked to won't do the job as is- it would need a check valve at least, so you may as well just use one from an auto parts store. You'll need to test pressure also. 8 psi is plenty.

 

[THALL10326]

head bolts are tight. no oil stains. i did install new head gasket. 8-10 tanks have been through it with no problems til today. the most confusing part, and probably the most telling symptom, is the verticle to horizontal 2 cycle to 4 cycle change. every time as quickly as 2 seconds from bar up to horizontal. didnt try rotating from bottom to side back n forth. just up and down.

dont own the vac/pres pump. i guess thats my next purchase. the saw can wait til. will this one work?

http://search.stores.ebay.com/MACNA...lterQ20PumpQ20wQ2fQ20PressureQ20GaugeQQsofpZ0

hey thall, this saw has your air filter flange on it! thanks again

1953greg

Awwwwwwwwww ok. Glad ya got some use out of it. Ya know I got a carb and other parts out there in the shed for a 460. Your welcome to the carb if you determind thats ya problem with ya saw. Must warn ya though its been sitting out there in the shed for over a year. Can't say for sure whether its any good. Its the new style, has limter caps on it. If ya think it will do ya any good just holler...................

 

[1CallLandscape]

i had a similar problem with my 026 turned out to be an airleak in the crankcase gasket causing a loss of vacuum pressure

 

[Dadatwins]

Cheap and easy way to check for air leaks can be done with some carb cleaner while the saw is running. Spray it around the carb rubber boot and seals and listen for tone changes. Sounds like an air leak problem, possible torn or misaligned carb boot, Spray not as accurate as pressure test, but it will find an air leak on a running saw quickly. Good luck.

 

[THALL10326]

Cheap and easy way to check for air leaks can be done with some carb cleaner while the saw is running. Spray it around the carb rubber boot and seals and listen for tone changes. Sounds like an air leak problem, possible torn or misaligned carb boot, Spray not as accurate as pressure test, but it will find an air leak on a running saw quickly. Good luck.

Good post there. Had a old timer tell me the exact samething.

 

[1CallLandscape]

yeah the spray was how i found my leak, works real well cheap and effective 99%

 

[Dadatwins]

Good post there. Had a old timer tell me the exact samething.

Now I feel old I learned the trick here on AS a while back working on a 036 that was driving me crazy ( short trip) trying to get the carb adjusted.

 

[THALL10326]

Now I feel old I learned the trick here on AS a while back working on a 036 that was driving me crazy ( short trip) trying to get the carb adjusted.

haha, well how old are ya by the way, mind ya now I'm a very young 48...

 

[1953greg]

update

i let the saw idle and used starting fluid to check for leaks. no rpm changes. so i let it warm up and more fluid. no changes. tried through a couple cuts, checked, and still no changes w/ the ether. so i tried to duplicate the movements and rpm changes and could not. tried for 4-5 minutes. problem gone! go figure??? maybe some trash n the carb?? seems as if it was under the needle seat it would b flooding not leaning. right?? i dont have a clue. maybe its gone forever. im sure not imagining things though. wasnt drinking either! i wil keep an ear out for it.

picked up a vacuum only pump from auto parts store. is it easier to cap the exhaust port and work on the boot side or vice versa? looks like the boot side wil b difficult to cap or attach either way. need to remove the carb? any help/directions appreciated.

thanks in advance 1953greg

 

[Lakeside53]

I find it easier to work from the carb side. Just undo the muffler screws a few turn and slip a piece of rubber inner tube material down behind the muffler then tighten again.

I have adapters for the carb (you take off the carb and fit the adapter) but it's pretty easy to make one out of a piece of aluminum plate or an old carb body. You can then just plug into the impulse line and you're ready to go.

The decomp valve on your 460 will leak under vacuum (gets pulled in). You can just take it out and plug it (stihl dealer will have the plugs) or try to hold it up with your finger nail...

 

[Dadatwins]

i let the saw idle and used starting fluid to check for leaks. no rpm changes. so i let it warm up and more fluid. no changes. tried through a couple cuts, checked, and still no changes w/ the ether. so i tried to duplicate the movements and rpm changes and could not. tried for 4-5 minutes. problem gone! go figure??? maybe some trash n the carb?? seems as if it was under the needle seat it would b flooding not leaning. right?? i dont have a clue. maybe its gone forever. im sure not imagining things though. wasnt drinking either! i wil keep an ear out for it.

Glad you got problem fixed, I would NOT recomend spraying ether at a running engine, VERY flamable, loose/bad spark wire/or coil and or a spark out of the muffler and KABOOM, a whole new set of saw problems, carb cleaner will burn but not ignite like ether. Be careful.