sleeves/hardness of bores

[Sam_Q]

once again a thread not related to Toyotas but bear with me

I am looking to make a cylinder sleeve for a two stroke engine. I am on a tight budget and so far my options are a Nikasil coating ($360!!) with any old sleeve, a 4 stroke sleeve and I cut my own windows or I machine something myself.

Does anyone know if aircraft grade 4130 cro-mo pipe is hard enough to do the job? Its only with a 47.5mm piston and this is what I would like to use.

I am leaning towards this as I have put a file to an old 4age bore and then did the same to a spare 4130 pipe, the 4130 pipe ws marginally better off.

[30psi 4agte]

I didnt think you want to go too hard with a material with the sleeve or the rings will never bed to the bore properly

[Sam_Q]

your right, although I am sure the ring would wear in somewhat quick seeing its super thin.

[slow laser]

i think ductile iron is what most car liners are (i think?)

what sort of motor is it?

[oldcorollas]

cast iron is often used because it has good lubrication properties due to the graphite etc and resists galling..

Nikasil is for aluminium bores no?

hardness is not always a desirable property for bores. friction, and oiling properties, plus gall-resistance, are desired.

but hey, give it a go and see if it dies

is worth searching around a bti on google
http://www.eng-tips.com/viewthread.cfm?qid=71974&page=4

random link http://www.cnczone.com/forums/showthread.php?t=46209

chromoly sleeve used here http://www.motocrossmechanic.com/sto...ct=parts_rhino

[Sam_Q]

laser: they are a grade of iron but still quite hard. I am working on an existing two stroke crankcase and looking to make my own barrel. It would end up being 58cc

corollas: cast iron is also used because in the right grade it can be made to be fairly hard, but yes your quite right.

Nikasil can also be used to treat other metals but the cost is the killer.

Although I know it was a comical statement I sure how this is right because I will be pissed if after all this work the thing dies on me.

The links you have found are great and I didnt think the info would of been that easy to dig up. I will keep looking around and thanks for the links

[oldcorollas]

no, cast iron is not hard. (cast iron is different from "iron")
"white" cast iron, where the carbon has formed Fe3C (cementite) is hard, but also very very brittle.

liners and cylinder blocks are made from cast iron with graphite flakes. it is not hard at all. it is soft, but not quite standard aluminium soft...

i thought nikasil was only used on aluminium, since the silicon is one of th eimportant elements from making Al "hard" (by forming silicon particles to reduce wear and friction).. i am not sure off hand what the solubility of silicon in Fe is, or if it will impart good properties.

sure it will work, bu tif it galls, it will die. with enough lubrication, it might survive.

also take on board the comment by Pat in the engtips thread... if the bore is not round (and it won't be), a hard bore will kill rings

[30psi 4agte]

Stew........ I wish i could just tap into your brain every now and then. I recon id be in awe by the shit that is in there

[oldcorollas]

it is just stock standard regurgitated metallurgy

[abently]

Go with the 4 stroke sleeve and cut/drill/die grind the windows in. Its a bit of work but not as bad as it seems especially with some reasonable tools and a good work space/setup.

[slow laser]

id use ballsa wood, nice and durable.


In all honesty it depends on the piston also? depending the material the piston is made of also affects the design of a liner? i mean we use brass liners in our 1/8th scale on road cars... wouldnt recommend it on a bigger motor though.

[Sam_Q]

brass? well that makes some sense as they have no piston rings right?

I think I will just run a 4130 bore and use a fairly rich oil mix like 25 or 30:1 with a synthetic oil.

[slow laser]

Yeah no rings is correct, But they also make unbelievable power... so the aluminium piston, brass liner works rather well (i think it was JP went to a AL liner but they wore out faster, also ran in faster too.. funny that)

but i somehow dont think yours is going to be cracking along with the same sort of power per liter


3.5cc 40000rpm = 2.9hp with three chambered pipes and restricted air filters (nirtomethane ftw)

[StuC]

the NSR250s i was working on all had nicasil coated bores, but they were a coating straight onto the cylinder and not sleeved. I have seen some sleeved items and recoated but they overbore and then re-sleeve. Call some perofrmance motorbike shops mate, they'll be able to point you in the right direction. Expect some dollars though - coating is not cheap

[Sam_Q]

your right the coating isnt cheap, I was quoted $260 for a Nikasil job.

abently: this is exactly what I was thinking and I will do some more enquiries as the first bike place I called just refered me to a custom sleeve place that wanted $300 just for a straight peice of pipe. Cutting the windows would be fine, just would need some patience as you say. I might even be able to do this with a dividing head on the mill, I would have very accurate ports then.