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Antique Gas Engine Discussion

IH LB 1.5-2.5 engine help


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  #1  
Old 02-07-2019, 05:45:34 PM
cajun1lung cajun1lung is offline
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Default IH LB 1.5-2.5 engine help

I just picked up a 1945 IH LB 1.5-2.5 engine and don't know much about it. The internals appear to be in good shape. Has compression and spark. The gas tank is rotten and needs some clean up on the mixer. I hope to try and start it this weekend after changing oil and cleaning mixer. Questions I have are.
1. When I spin engine over I hear a loud clang from magneto every time the magneto fires. Looking inside the magneto all looks good and I see the piece snap causing clang. Looks like that is what it should be doing. Is this normal?
2. When I roll engine backwards it comes to a sudden stop like there is a catch that stops it from spinning backwards. Is this normal?
3. How much compression should there be? There is compression when I spin the engine over, valves seem to be operating. Should it be kind of tough to get past the compression stroke when spinning engine over?
Thanks in advance for any advice.
I am new to this forum and these old engines. I have always enjoyed watching them run. This was an old barn find on a property I used to hunt. I am glad I was allow to take the engine as the barn is now collapsed.
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Old 02-07-2019, 06:08:46 PM
forney00c forney00c is offline
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Default Re: IH LB 1.5-2.5 engine help

Welcome to the Stak! The clanging noise coming from the magneto is the impulse, and it is normal. It helps give a hotter spark at low RPM for starting, but will disengage once the engine is running.

These old engines are low compression. I've heard several times that if you spin the engine against compression and let go of the flywheel, it should bounce back. If it doesn't, then you'll want to look I to valves and possibly rings.

As far as the catch when turning it backwards, I'm not too sure what to think about that. You should be able to spin it backwards easily until you come up on compression again.
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Old 02-07-2019, 06:42:46 PM
cajun1lung cajun1lung is offline
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Default Re: IH LB 1.5-2.5 engine help

Thank you for the quick response. I thought this was normal for mag but wasn't sure. It doesn't bounce back on a slow spin when it gets to compression stroke, I will try to start like it is before tearing into it.
Yes it definitely hits something solid when I roll it backwards after about 1 revolution. I pulled the inspection cover off but didn't see anything that looked broken inside. Although I didn't spin it over while looking inside.
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Old 02-07-2019, 06:51:11 PM
Pat Barrett Pat Barrett is offline
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Default Re: IH LB 1.5-2.5 engine help

And I'll try to give you a pointer. Be very gentile with the brass nut that screws into the mixer/carb. The threads in the carb are easy to strip as the body is pot metal like. Same goes for tighting it back up.
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Old 02-07-2019, 08:13:44 PM
Jeremy Hartle Jeremy Hartle is offline
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Default Re: IH LB 1.5-2.5 engine help

Pats rite. Be careful with that pot metal mixer. Messing the threads up is real easy. I wouldnt try to start it though until you determine why it wont turn backwards.
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Old 02-07-2019, 09:02:58 PM
cajun1lung cajun1lung is offline
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Default Re: IH LB 1.5-2.5 engine help

Ok, thanks for advice. I will pull cover and drain oil and take a good look inside. The mixer is actually in good shape. I pulled needle and fuel line out and they came out easy. I noticed the choke cap appears to be pinned and not removable. A lot of crud in breather box falling out. Unless there is a way to take the choke cap off, I will have to do best I can to clean inside.
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Old 02-07-2019, 09:40:11 PM
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Mike in NC Mike in NC is offline
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Default Re: IH LB 1.5-2.5 engine help

Welcome to the Stak!!

Our LB will turn backwards until it comes up to compression and it stops.

Below is a link to a PDF manual for the LB.


IHC LB Manual
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Old 02-07-2019, 10:07:43 PM
cajun1lung cajun1lung is offline
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Default Re: IH LB 1.5-2.5 engine help

never tried to spin backwards fast, but if I roll it backwards after about one revolution it stops suddenly with a metal to metal clang. I read one post where one guy had a broken govener but didn’t mention anything about spinning it backwards. I have never had a reason to spin an engine backwards, but I spun it backwards accidentally and saw what happened, so I did it again not knowing if it should or shouldn’t and it does it every time.
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Old 02-08-2019, 08:54:46 AM
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Default Re: IH LB 1.5-2.5 engine help

The impulse pawl on the mag might be what is causing the engine to turn not turn backwards. You could remove the mag from the engine and roll it backwards to see if this eleminates that issue. You will however be taxed with having to time the mag back to the correct position when you reattach it to the engine. Just a thought.
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Old 02-08-2019, 09:04:34 AM
cajun1lung cajun1lung is offline
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Default Re: IH LB 1.5-2.5 engine help

Thanks. Was wondering if that might have something to do with it. I will look over everything close before trying to start. Thanks for everyone’s input. I hope to have it running soon. I will post pics as soon as I figure out how to.
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