BR600 carb air leak

[ol'homey]

When priming my BR600 the primer bulb is always sucking air no matter how many times you push it. I tried a new bulb with the same result. Then I tried a few tests:
Test 1: Bypassed the carb by connecting the fuel line from the tank to the inlet of the primer bulb. Works great! Bulb fills with fuel, no air. This eliminates all the hoses and isolates the carb as the source of the air leak.
Test 2: Pressure test carb: Connected the outlet of the primer bulb to the carb fuel inlet and to a pressure gauge with a T fitting. Pumped primer bulb up to 20 psi. (didn't expect the little primer would do 20 psi but it did!) Pressure held, needle didn't budge.
Test 3: Vacuum test carb: Connect inlet of the primer bulb to carb outlet connection. Connect vacuum gauge to carb fuel inlet. Pump primer bulb. It showed a slight vacuum maybe 1" Hg but it did hold.

Did the carb fail the vacuum test? If so, where is it leaking? Metering diaphragm/gasket? The fuel circuit all the way to the needle valve is holding 20 psi so none of that could be leaking right? The blower starts and runs with the carb like this. Heck for all I know maybe it's supposed to always suck air through the bulb when you prime it? Any ideas Lake, Tom, Bueller, anyone ........

 

[Lakeside53]

Internal check valve stuck open. Usually new carb time... You might try ultrasonicaly cleaning it...

If it's less then two years old, it under warranty (either homeowner or "emisson component").

 

[ol'homey]

Thanks Lake, I didn't think it was right but I've never seen a carb like this before. I've got the IPL and see parts 44,43,42 which is a pump piston, seal and spring. Is this the internal check valve? If not, any idea what these parts are for? Also what effect does the check valve being open have on operation of the blower other than the primer sucking air? Is it OK to run it like that until I find another carb?

 

[Lakeside53]

The check valves that fail are non-replaceable and not shown on the ipl - they are provde mid-range and L transition. You are looking at the accelerator pump. It could be that, but not usual in my experience.


That carb is strangly quite inexpensive... $46 MSRP...

As for running it... "Probably" o.k... but...

 

[ol'homey]

Local dealer has part # 4282 120 0604 for $47.40. This is supposed to be an updated carb. Also put a call into Stihl and the tech sent me to Mid Atlantic Stihl for warranty claim. He thought it should be covered but said it was up to them. Left a message for Brice at Mid Atlantic so I'll wait to hear back from him.

 

[ol'homey]

Brice called me back and said it's out of warranty but he will warranty it as a "customer satisfaction" claim. He said take the whole unit to Grand Strand Power and if they find it has a leaking internal check valve he will warranty carb replacement and labor. So I took it in and showed Mark the service manager the air bubbles in the line between the carb and primer, and the air in the primer that never clears because it's sucking air due to the stuck open internal check valve. Mark said the air could be due to a number of things and he would have to have a tech check out the carb. Since there was no tech in the shop today I would have to leave it. So I went in sure it was a leaking internal check valve which Brice would cover. After agreeing to pay the $27.50 diagnostic fee if they somehow found it was not a leaking check valve, I left not knowing if it was going to be covered or not. So I'm gambling $27.50 that they are going to come to the same diagnosis that Lake did. I'm not feeling very lucky so now I'm thinking maybe I should have just bought a new carb for $47 saved the $27.50 diagnostic fee and been done with it. I'll keep ya posted......

 

[ol'homey]

Test 4: Check primer bulb vacuum. Connected inlet side of primer bulb to vacuum gauge. Pumped bulb a couple of times and it's holding 7" Hg. I used my old primer bulb since the new one is on the blower at the shop. Pulling vacuum on the carb I could only get around 1" Hg. So the carb is clearly leaking air. Now let's hope they agree!

 

[rmh3481]

Hey Ol'Homey,
How did you feel about that diagnostic charge? Especially after being sent there by Stihl?

Im telling you the truth when I say that B/S grabs me in the wrong place.

I had a problem with a HVA blower that I bought in Texas while on business. The unit developed a bearing 'death rattle' after it was 6 months old. I took it into this new place that is out my way in Pa and they say to me, $37.50 diagnostic fee for a warranty claim. I had my receipt but hadnt bought this unit there. I know your supposed to get that money back, but I still think it is bad business.

 

[ol'homey]

Well you guys are NEVER gonna believe this. Got the call this AM, blower is fixed and running good. A Stihl instructor gave a class at the shop last night and used the blower as a teaching tool, so there is no charge. OK great, what did he find? The valves needed adjustment and a fuel line was twisted. What about the carb? Carb is fine, no problem. Did he do a vacuum test? Dunno. I say it's got a leaking internal check valve and will fail a vacuum test. Mark says the blower won't run with a leaking internal check valve so there's no way it could be leaking. I say go to Arboristsite.com and look at this post and you'll see a Stihl tech on there called Lakeside who says it will run with a leaking internal check valve. Nope, won't run like that..... I go pick up the blower. Push the primer bulb and now it's almost full of fuel and not sucking half air half fuel like it did before. I say yeah it is priming a lot better than it was before. I told Mark I was going to vacuum test the carb again and asked what vacuum it should hold. He said about 7" Hg for at least 20 sec. Made perfect sense to me as that is what the primer will show when connected directly to a vacuum guage. Took the blower home, put it on the bench, took the cover off. First thing I notice is the gasket that is supposed to go between the air filter housing and carb is........now between the carb and intake boot! Took a couple of pics but they are over 1 Mb which is too big to upload here. They wouldn't prove anything anyway. There is not supposed to be any gasket between the carb and intake boot, just the metal ring and the intake boot itself. Pull the fuel line off and attach vacuum guage. Push primer a few times and guess what......it's now holding 7" Hg just like it's supposed to. Before I could barely get the needle to move. Did the internal check valve unstick itself? Put it all back together. It's priming like it should now, runs OK, WOT varies from 6900-7200 depending on how the hose is bent. Hose straight out 6900-7000, hose bent like up like you are storing it, 71-7200. So it depends on airflow, but I have a question: Could running 89 octane with 10% ethanol cause a decrease in WOT rpm from the 7200 rpm spec? Also both H and L screws are set fully CCW at the limiter stops.
Lake any thoughts on the above. I do know 2 things for sure (1) the blower was running, it just wasn't priming right, sucking a lot of air and (2) I could not pull a vacuum on the carb before I took it to the shop. Any thoughts?

 

[Lakeside53]

I'm betting the valve just unstuck or cleared out some debris.

It's a 4 stroke, so tuning is not like a 2 stroke... and the H&L screws only control a small % of the fuel flow.

If you can't pull 700-7100 it's just getting a bit worn out. The only way to check is to do a leakdown test. I assume they used edta to clean the gunk off the valves before adjusting?

Are you using a pure synthetic mix oil? You should be...

E10 is not an issue.

 

[Lakeside53]

Hey Ol'Homey,
How did you feel about that diagnostic charge? Especially after being sent there by Stihl?

Im telling you the truth when I say that B/S grabs me in the wrong place.

I had a problem with a HVA blower that I bought in Texas while on business. The unit developed a bearing 'death rattle' after it was 6 months old. I took it into this new place that is out my way in Pa and they say to me, $37.50 diagnostic fee for a warranty claim. I had my receipt but hadnt bought this unit there. I know your supposed to get that money back, but I still think it is bad business.

I see it from both sides, but in this case it was out of warranty... but they were ready to supply the parts only for free.

 

[ol'homey]

Just started using the synthetic oil and will from now on in everything. Just keeps everything a lot cleaner inside. On the diagnostic fee I lucked out this time and they didn't charge me. But like Lake I can see both sides. Thanks, Lee

 

[ol'homey]

Back to square one. Primer sucking air. Push primer bulb and it pops right back out pulling air instead of fuel. Internal check valve stuck open again.
Mid Atlantic Stihl won't allow me to take the carb to the dealer and do a vacuum test right there on their counter to show them it won't hold a vacuum. That would just be way too simple. Instead they have to have the whole unit and their tech will diagnose what the problem is if any. Already tried that route. Took it down there, told the service manager it had a leaking internal check valve, showed him the primer was sucking air. Said he'd have a tech check it out. Got it back and the primer WAS working great. Don't know what they did to free up the check valve but they did get it working again for a day. Now it's stuck again. Any ideas what to do now?
Mid Atlantic said they would replace carb if it failed a vac test, but how do I get them to see it fail a vac test? Apparently there are Stihl instructors all over the area. Could I get one to stop my house? I'll make this deal with Stihl.
Send a tech to my house, do a vac test on the carb in front of me. If it fails give me a new carb, if it passes I'll post here that I'm an idiot and was just imagining the whole problem. Anybody here got enough pull with Stihl to get a tech to Myrtle Beach? Maybe one that likes to play golf?

 

[CentaurG2]

Spring clean up is coming. Time to give that 4-mix thing the flush. Go out and get yourself a redmax 8001. Its like having a 372xp strapped to your back. Heavy and drinks fuel like a Holly 4barrel, but it will dethatch your lawn and you will never want for more power. Pricy, cost you about $100 more than that stihl but you just cant beat a 2 stroke!

 

[ol'homey]

I give up! Used the blower for about 40 min today. Looked at the primer bulb, it's almost full of fuel. Pushed it a few times, working fine again, sucking fuel just like it should. I guess maybe the heat and vibration from running it was enough to soften whatever varnish etc. was causing it to stick so for now it's working again. I like a lot of things about this blower. I use it to clean up thousands of sweet gum balls in my St. Augustine grass yard. My old BR400 just didn't have enough power to do the job. The BR600 has enough power and it's comfortable and only about 5lbs heavier than my BR400 I think. The 2 problems I have with it are (1) it's a bear to pull over as the compression release on the cam isn't working. Everybody says adjust the valves because if the intake valve adjustment is loose the mechanism won't be able to lift the intake valve during starting to bleed off some compression. Well I've adjusted the valves with the stihl feeler gauge and so has a Stihl tech and it still is just as hard to pull over as ever. I've got a new cam wheel and will replace it soon which should solve this problem. (2) the intermittent problem with the carb internal check valve sticking. Keep in mind that this blower has seen 3 seasons of commercial use and might have 1500+ hrs on it. So most people won't ever see the problems I'm having. The good news is that when I got it and pulled it apart to replace the pitted original steel exhaust valve with the updated Stellite valve the first thing I noticed was how little wear there was on the piston skirts (machine marks still visible) and on the cylinder bore (light hone marks still visible). I don't think you will see this after 1500 hrs on most 2 stroke blowers. So I put a new ex valve, rings, and crank seals on it and it runs good (turning 7100 rpm WOT which is about where it should be today when it used it). So I think it will be a decent blower if I can get a couple more kinks worked out.

 

[Lakeside53]

Hard to pull over usually means the exhaust valve seat is carboned... if you've not used synthetic mix until now I'm suprised it made it to 1500 hours. I'd be doing a leakdown test also..

Adjusting the valves without getting rid of the carbon is a waste of time.

EDTA treament (careful...) followed by a valve adjust, then hot run and another valve adjustment will almost always let your decomp work correctly...

Run synth and you won't get carbon on the valve seats.

 

[Martinm210]

Glad it's working for you. I love my new BR-600, only ran a tank of gas through it so far, but all that power is such a treat. I was able to clean crab apples and kids toys, everything off the yard. It even strips snow/ice off the driveway really well.

Snow blower...who needs something with wheels?...

Next to my saws, one of my favorite new tools.

 

[ol'homey]

Lake, I bought it used for $75, no compression, with new straps and recently replaced tubes/bellows. Ex. valve was steel and was pitted causing the loss of compression. Tons of carbon in it as the previous owner ran Stihl orange bottle in everything. I cleaned all the carbon out of it when I installed the new ex valve, rings, and seals. With the valves adjusted with the stihl gauge it will still show 150+ psi compression. That's why it's hard to pull over. I think if the compression release was working it wouldn't be that high. All that's left that I know of to change is the plastic cam wheel. Maybe the mechanism the pops up the little nub is sticking due to all the carbon that was in the crankcase? (didn't try to get the carbon out of the cam as I didn't want to hurt the plastic). Or maybe after 1500 hrs the little nub is worn down a little and not lifting the intake valve like it should?

 

[ol'homey]

Lake, the part # for the cam wheel in my ipl is 4282 030 1801. The part # stamped on the cam wheel I have in my hand is 4282 038 1803 A. Can you confirm that what I have is the correct cam wheel for the BR600. Just want to make sure before I install it. Thanks

 

[Lakeside53]

yes, the 1801 is the correct part number for a BR600. The -1802 is for the 500. 1803? hmm... no such listing... Sometimes the part #on the plastic can't be relied on for id. For all I know the 1801 and 2 are derived from a common plastic part - the 1803...

You can see the decomp working if you very slowly turn over the engine by the flywheel with the valve cover off. The valves will cycle normally, but around TDC there will be a tiny "jump" in the exhaust valve.

Sorry, thought you'd run it for the 1500...