Honda JC30E engine rebuilt

[kon rad]

Could anyone tell me if it would be OK to use intake and exhaust valves with 5.5mm stems if the original valves had 5mm stem?
The engine is Brazilian made Honda JC30E engine.
Thanks

[unitynotsocri...]

If the valve length and valve size are the same then it should work if the valve guides are bored out to match,valve stem seals should not be a problem......,

You must check the valve in its seat to see if it needs recutting or grinding.
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS

[kon rad]

These valves(Chinese clones) are exactly the same as original Brazilian ones except for the stem diameter. And cost 10x less, literally...
Boring out valve guides you mentioned sounds complicated and expensive. Would polishing stems down to 5.1mm do the job?

Would you happen to know how critical for the operation of camshaft is the flow of oil through the channel shown in the attached picture? The reason I asked is that there is an over sized barrel that will fit my crank case, but the match is not perfect in the camshaft area(see attached picture). My thinking is that although the amount of oil through that hole will be reduced, the amount of oil from all other directions should be enough to keep camshaft going. Does that make sense?
Thank you

[unitynotsocri...]

They are not exactly the same....they are ten times cheaper . grinding off a few mm will make them behave even cheaper ! They may be wideer cos of crappier steel.
I d check the valve guides and see if its possible to swap them forchinkojap ones.

You may get back pressure in the oil supply and a leaky head if you restrict the oil feed.,.but....! Just kid on its an old Brit bike.no one will know.

If the barrel ally can be chopped so the oil hole is clear then do it. Beware......many big bore kits sometimes need the crankcase mouth to be rebored and some have mismatching lower barrel liners . You can't really go up more in cc terms for the effort\ money involved .

Check the valve guide sizes ,if you can't fit chinklyjap matching guides you could get an engineer to bore out new Honda ones...

Please be careful when mixing chinklyjap and jap parts. There's a few differences between the Honda cg . Generally just use the chinklyjap cases\ covers. The internals are not exactly the same.

You may be able to refit knew guides using the oven to heat the cylinder head ,
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS

[kon rad]

Thanks , it sounds reassuring as I didn't seem to miss any obvious points to consider.

[unitynotsocri...]

The steel piston liner.....in the barrel can be too long and touch the crank or not fit the crankcase mouth.

When it comes to jap vetrsus chincrap I think of Russia and Germany slogging it out on the eastern front. The Germans with quality network and great optics ,bombs,training etc wheras the ruskies had to stick with bolt action rifles,planes made from fabric but.........win by producing ten times the numbers.

One should compare a Honda seventies\ eighties cg engine with a chinklyjap one.
One of the first things you notice is 8 mm engine\ casing bolts rather than 10 mm head . times that metal saving by the million ....like the ruskies in ww2 and it adds up.
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS

[kon rad]

Oh, now I see what you meant by