kempy Posted September 29, 2017 Share Posted September 29, 2017 I have a nitro engine that's NOS , unused but by the feel and look of it I think the bore sleeve is slightly crushed out of shape at the top, causing the piston to bind, this isn't substantiated yet as I don't have the measuring gear to substantiate this, only an eyecrometer. I'd really like to get the engine going but lack the kit to measure and machine, does anyone here have a small accurate lathe at their disposal ( Pref Akl.) I'd love to own a small lathe, but alas.. Im not sure what tolerances to use or even how to bore an engine this small, but any help would be greatly appreciated CHeers Kempy Quote Link to comment Share on other sites More sharing options...
M.H. Posted September 29, 2017 Share Posted September 29, 2017 Most glow engines are ABC, aluminium piston, brass liner with a chrome bore. Usually when they are brand new they can be very tight. What brand and size is it? Quote Link to comment Share on other sites More sharing options...
kempy Posted September 29, 2017 Author Share Posted September 29, 2017 Its a GMS 2000, 0.4 cu in. You're right with the ABC setup but it's so tight that I can't turn it over by hand ie. The piston moves freely for the bottom 80% of the stroke?? Quote Link to comment Share on other sites More sharing options...
hohocc Posted September 29, 2017 Share Posted September 29, 2017 Might be worth posting your question on rcgroups.com or rcuniverse.com, there must be tens of thousands of those engines out there and someone will have struck this issue. 1 Quote Link to comment Share on other sites More sharing options...
M.H. Posted September 29, 2017 Share Posted September 29, 2017 1 hour ago, kempy said: Its a GMS 2000, 0.4 cu in. You're right with the ABC setup but it's so tight that I can't turn it over by hand ie. The piston moves freely for the bottom 80% of the stroke?? How big is the flywheel, I have a CMB .21 that feels like that just because the flywheel is hard to get a grip on 2 Quote Link to comment Share on other sites More sharing options...
tortron Posted September 30, 2017 Share Posted September 30, 2017 What's the bore size? I have some bore gauges but prob not small enough? 1 Quote Link to comment Share on other sites More sharing options...
M.H. Posted September 30, 2017 Share Posted September 30, 2017 Will be around 20mm Quote Link to comment Share on other sites More sharing options...
kempy Posted September 30, 2017 Author Share Posted September 30, 2017 Yes, 20.5mm according to a parts list I just found. I'm just trying to turn using the prop mount without the glow plug in and a few drops of ATF I honestly wouldn't think it would be that tight? Quote Link to comment Share on other sites More sharing options...
tortron Posted September 30, 2017 Share Posted September 30, 2017 Ahh bugger, smallest is 50 1 Quote Link to comment Share on other sites More sharing options...
kempy Posted September 30, 2017 Author Share Posted September 30, 2017 Have found some sites mentioning the sleeve was super tight, put the engine in a vice and turned it over ok, I just wasn't expecting it to be that tight. cheers @00quattro00 & co. time to get this puppy working! Quote Link to comment Share on other sites More sharing options...
NickJ Posted October 1, 2017 Share Posted October 1, 2017 Can someone confirm/deny something in my memory from years back says these little motors had a slight taper? 2 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted October 1, 2017 Share Posted October 1, 2017 I do know they wear very quickly. And are expected to go out of tolerance fairly quickly. I worked with a guy who raced nitro buggies. To save on rebuild costs he had machined a tool that would accurately crush/ squeeze the liner to get the bore back into tolerance. Seemed to work pretty well! ( He also machined his own heads with huge heatsink fins so he could run more aggressive fuels) 1 Quote Link to comment Share on other sites More sharing options...
sentra Posted October 1, 2017 Share Posted October 1, 2017 Swing by if your still wanting to measure it - unsure how you would go at honing a chrome bore? But your welcome to use my lathe etc 1 Quote Link to comment Share on other sites More sharing options...
M.H. Posted October 1, 2017 Share Posted October 1, 2017 1 hour ago, NickJ said: Can someone confirm/deny something in my memory from years back says these little motors had a slight taper? Yep slight taper 1 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted October 1, 2017 Share Posted October 1, 2017 definately try running it first before you go bore it larger and fuck it LOL 3 Quote Link to comment Share on other sites More sharing options...
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