SR450 Mister Bogging

[lefty]

So I got this in from a friend. A little long in the tooth and has never been serviced, but in use. Has a bogging issue so I inspected it and usually stock a carb or two for it. Threw one on for testing, dumped the fuel, and inspected everything, lines, filter, spark arrested, ports for carbon, etc. Still bogging when throttling up. So I figured I would start digging deeper and I'd best start looking for leaks but wanted to check compression first. When releasing the pressure from my compression tester, a bunch of yellow oily goo came out of the valve. It looked and smelled like oil, like regular motor oil. The plug, the cylinder, and this substance smelled nothing like gas. So I thought I'd take another run at it. Checked everything again, purged the fuel, ran it again and it bogged. So I stuck my tester hose on it again and the same thing. A yellow oil was coming out of the compression tester.

I'm wondering if something is pooled up in the crankcase. This is weird. It's not a machine that has been sitting around. It's been in use. I've seen and smelt bad fuel in machines before but this is different. Dare I classify it as a foreign substance?

However, the customer is a friend but the user is an employee of his and I haven't spoken to him. But putting something foreign in the machine would be unlike this employee. But I don't have a full chain of custody is my point. If this stuff is coming out of my tester, it's no wonder it's not running right. Any opinions are welcome. Thanks.

[KE4AVB]

Stihl 4244 Engine. Going to be the same engine as the BR450. I don't a specific service manual for the SR450 but do have one on the BR450.

And yes you are going have to clean the crankcase of excess fuel load. The yellow stuff I have no idea what it is as haven't seen any fuel mix that color here. It also sounds you got carburetor problems. It is a Zama C1Q-S165 which would need a RB-161 repair kit. You need to go through CTS on Amazon to get a kit as the dealer around are not able to get Stihl 7010 871 0222 OEM repair kit just a GND kit instead or a complete carburetor. It appears the US Stihl group refuses to provide the full repair kits. And can't get from Zama distributors as Stihl has barred Zama from selling them through the distributors.

Now there are few other vendor providing cheaper kits but I do the CTS are good ones. The other after markets I haven't tried.

Now if you want I can send via regular email the BR450 4244 engine service manual.

And here is the carb tuning info. These are initial settings. Idle speed is 3000 rpm.

[lefty]

Thank you for that offer. I'll send my email to you.

[KE4AVB]

SM sent to your registered gmail address.

[lefty]

Thank you

[lefty]

Looks like I have a leaky seal on the recoil side. Unfortunately, I don't think I'm going to get the opportunity to work on this one because I don't see this customer fixing it. He tends to just buy a new unit when anything significant presents itself. Thank you for the help. The service manual was very helpful.

[KE4AVB]

That seal is a TC15x25x5 seal and doesn't look it is a captive seal so it should be easy to replace without completely tearing down the engine.

Yes I know that Stihl list the seal as an "AS" but they are the same as the TC seals.

[lefty]

I guess I could replace that one and see if it still leaks then. Looks super small though. Any tips on removing it? I can see that they used a sealant.

[KE4AVB]

Sealant is applied the crankcase pieces but around the seal, just up to them. Personally I have tried pulling one those seals yet as I have yet to ran across an unit needing them replaced yet. As you tomorrow is another day that anything can happen.

But I have pulled smaller seals from Kawasaki engines but I made my own puller for those. I know a lot DIYer suggest using screws but they can damage the crankshaft.

[lefty]

It certainly is a small one. I have a few misc tools designed for pulling seals. Maybe I'll get lucky. Thank you.