Stihl BR 500 blower with low compression 60 psi

[EngineMan]

Are you doing the test with the throttle full open..?

 

[stumpfg]

valve adjustment is very important. I think it is .002 for both vavles

 

[sinful619]

Are you getting anything at all when you try to start the blower, is it turning over or acting like it wants to start or is it just flat?

Completely flat.

i think i am right in saying you need more than 70 psi for it to work and that still not run as it should but please some one on here will confirm if i am right i think i seen this some where on the net

i would first try about 3ml of fresh fuel open the choke tip the unit on its side pull the throttle and drop the fuel right in there so it goes in to the chamber (you will have to take the air filter out first) close the choke so it full on and try starting it its should start fairly easily if its starts it prob is worth playing with if it dont and you know the psi is low then sell it for spares they do go fairly well even not starting

if it starts and runs for 2/3 secs then you have to decide if it needs more than a strip down carb cleaner and an air compesser( do not get the carb cleaner on the rubbers as it will rot them) or if your in usa prob better to but new carb as have seen they sell cheap there if your in uk you might want to take a seat before ring for a price its about ｣90 for a carb a new sthil is only ｣150 lol

hope this helps but there will be someone hear with more know how than me thanks angel

I have not try to poure fuel directly in the carb. might be the next thing although the entire blower is taken apart now with the exception of the engine against the plastic shield/fan. I can't take the fan bolt off but just found out a piston stop tool is necessary.

when I went to a stihl service school back in 99,lol...they could've cared less about compression testing,they wanted a crankcase vacuum/ pressure test,..after I checked the spark arrestor screen,id pull the muffler and carb and check the condition of the cylinder wall, and piston if a ball pont pen cant feel any scratches neither can the ring, hope that helps

yes but I still need to know what the 60 psi reading is and why.

Are you doing the test with the throttle full open..?

Yes with the throttle wide open.

valve adjustment is very important. I think it is .002 for both vavles

I adjusted the valves differently for testing purpose: first tighetened both to 1/4 turn and did a compression test with 30-35 psi result. then went back to the original position and got back 60psi. loosened the valves this time 1/4 turn and got the same 60 psi result (valves pretty loose at this point).

I don't have a thin enough feeler gauge so that's the method used so far to see if the compression would change.


I'm really lost here.

 

[Rokon]

I don't have a thin enough feeler gauge so that's the method used so far to see if the compression would change.


I'm really lost here.

You need a special feeler gauge, Stihl was very crafty in their engineering.

You backed the valve lash off till the rockers are loose, and still have 60 PSI? Doesn't sound good.

By your descriptions I am leaning towards a scored cylinder.

 

[taxidermist]

Dont worry about compression as they have a compression relief and you will not get a good reading. Always do a leak down test to make sure valves are sealing. You can get the feeler gauge at a dealer for $.50

I have a 4 mix that is also a no start and I have tried a good carb, cleaned the valves, lashed the valves. I have been told that there was a problem with the ing module so I will try that next.

I am not really a parts replacer but this one has me stumped!

Rob

 

[sinful619]

Hi all,

I have not been able to remove the fan bolt without the piston stop tool. I tried using the small rope method inside the cylinder and is not working for me.

No leak down tool here. Do you recommend any? do an automotive leak down tool work for a small engine? And have you've try to get compression reading just to see where it's at?

 

[sinful619]

after taking the motor apart the problem seems to be carbon build up on the exhaust valve and seat. I just finished cleaned everything up and used some lapping gel to properly seat the valves again.

I'm placing everything back together and not sure how the ring gaps should face...this piston doesn't have dowels for the ring gaps.

 

[EngineMan]

This should help you out.

 

[sinful619]

ah nice thanks it says 120 degrees but I didn't think about getting a reply so went to 180 degrees instead of 120 and engine is all sealed up now. you think those 60 degrees off might give problems? On this cylinder the ring end gaps don't pass through intake or exhaust ports.

My next step is doing the valve adjusment..

 

[taxidermist]

Dont worry about compression as they have a compression relief and you will not get a good reading. Always do a leak down test to make sure valves are sealing. You can get the feeler gauge at a dealer for $.50

I have a 4 mix that is also a no start and I have tried a good carb, cleaned the valves, lashed the valves. I have been told that there was a problem with the ing module so I will try that next.

I am not really a parts replacer but this one has me stumped!

Rob

Fixed mine!

http://www.lawnmowerforum.com/stihl-forum/18987-stihl-tech-help-110-r-4-mix.html