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Hard Start B&S 15hp industrial

712 Views 11 Replies 8 Participants Last post by  Tom-machinery-idiot

I own an old Scotts S1742 which I repowered with a B&S 15hp. It is not an Intek, it's an old Commercial & Industrial which came out of a Troybilt. The engine started and ran fine before I removed it from the Troybilt. Now that it is in my Scotts, it is hard to start. The engine needs to crank for about 30 seconds before the first ignition, and then another 30-45 seconds of cranking with intermittent sputtering before it will stay running. I need to start it at low idle, let it warm up for about 30 seconds, and then slowly bring the throttle up to operational speed.

- I tried adjusting/tightening the valves, it has made no difference.
- I tried tweaking the carburetor a few times. It is currently tuned well, but I have it running a smidgen on the rich side just to keep the engine from burning up.
- The choke is useless. If I try to use the choke, the engine simply will not start. I just leave the choke off.
- I believe the carb is the one which came with the engine, although I can't recall since I did the swap over a year ago.
- The troybilt had a choke which was separate from the throttle. The scotts had one of those setups where you could choke it by pushing the throttle all the way up. I couldn't really get it to work the same after swapping, so I installed a separate choke cable and lever, which I bolted onto the side of the steering column.

Once the engine is running, it runs very well. If the engine stalls while hot (e.g., running out of gas), then I have to set the idle low again to make it start, but it does not need to crank a lot like when it is cold.

Any ideas?
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What a combo of symptoms. The need for a lengthy crank cold is indicative of lack of fuel in most cases. The hard start warm, and need to set at idle speed, indicates that it may also be lacking fuel as a wide open throttle plate will try to pull fuel ... that may not be there, so it won't even fire, as the mix is too lean.
I would check for a good flow from the tank by removing the fuel line from the carb, and catching the flow in a proper container. You should get full-tube flow of gas if it is gravity fed. No restrictions. If you have a clean fuel line, filter, and you get a slow feed, you might have a too-restrictive fuel filter. I have read that pumped system filters are more restrictive than gravity fed, but don't bet your paycheck.
Any way, you should get a full-diameter flow in either case. If you get that, then pull the float bowl and check that the float will drop properly, and there is not crud in the float valve.
One other thing is that an engine with valves adjusted too close may be difficult to start hot. The clearances close up, and may not allow good valve seating. If you ask around here, you can get instructions on valve adjustment. I think Walter has them available via email. Crankshaft to be at 1/4" past TDC to adjust OHV engine valves, from readings.
Does the installed carburetor have an adjustable 'main jet', or is it fixed? Most are fixed anymore. The idle mix is still adjustable on a lot. The idle mix is used as a 'transition' mix for the engine to accelerate to operating rpm without misfire, FWIW. If too lean, you will likely get stumble and hesitation as you advance the throttle to operating speed.
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