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[Scalyback]

I think my intake valve may be sticking open once in a while.



this is due to two times when I have had no compression during starting proceedure, and one time when Tornado managed to blow the bloody carb straight off the engine.



Does he need a clean or decoke, or should I be looking at new valve guides as standard here guys?



"My bike wants for nothing, except maybe a bloody good kick!"

[Tim NZ]

Normal oil consumption is 1-2cc per km traveled.
Excessive is over 3cc per km traveled.
Carb blowing off? Ignition timing over advanced.

[mauri]

to the over advanced being a probable cause you can also ad an air leak in the intake manifold as a possible culprit.

[slowmo]

I am in a similar position with my 10 Kmile 500 iron barrel - there has clearly been an issue with carb jetting in the past that has resulted in the inevitable burnt exhaust valve, recession and excessive wear to guides, rocker block and possibly pushrod (hint of a slight bend). Not my fault Guv, honest just happened on my watch! Oil burn was not excessive and not realy detectable in the exhust - most seems to puke out of the crank breather resulting in a very well oiled chain.

Have resolved to replace all exhaust side components. I am 99% sure that I am the first to have taken the head and barrel off this one.

However, picking up on TimNZs comments on pistons, I noticed on mine the slight pinching of the oil ring in the bottom groove. Beacause everything else appeared in good condition and well within limit, I gave the the upper part of the piston a gentle scrape on the lathe of a thou or 2 to ease the scraper ring. I was going to change the piston and rings, but because the item supplied by mein host appears to be exactly the same as the stock item I have, I assumed it is the same as normal Indian factory piston, and would be no better than my existing item.

In all other respects pistons and rings seem in remarkably good nick for 10000 miles, with no scoring or wear and are original size (so not been rebored).

Is it the general wisdom that I should cough up the extra £100 for new piston and rings etc and face the bother of running them in, or could I make do with what I have for another 10k miles? appreciate the collective wisdom of this site!

[Bullet Whisperer]

Hi Slowmo, if the top breaks off that piston, all hell will break loose in your engine and it will cost more than £100 to fix. If you want another ten thousand miles, best put a decent piston in there. Cheers, Paul.

[Thack]

Ivor writes: "The problem with this engine was a high petrol consumption and medium oil use. I top up oil every 200-300 miles and only get low 50`s mpg."



Ah hah, a clue! Ivor, I think the soft carbon you report in the combustion chamber is because the bike is running too rich, and that explains the poor fuel economy, as well. So I would certainly look to your carburettor for problems.



That doesn't affect the oil consumption, though, and I can't add anything useful on that.

[PeteF]

I'm not sure about those valve guide seals - surely it's better to have a trace of oil in the guides?

[Norm]

Please don't get Tim started on piston failure,he talks in hundreds. lol Tim solved the problem for many some years ago by getting JP pistons to manufacture what was dubbed the Busby spec piston. No idea how many I have fitted over the years and I only know of 2 failures and they were due to other engine problems. I have also had good results with our hosts American high comp piston but that only comes in +40 so requires a rebore to fit

[slowmo]

Thanks for the advice Norm and Whisperer, Think I wiil go for a new piston to avoid the false ecomomy. Not sure of the merits of the 'european made' piston that looks suspiciously like my 'Indian made' piston, versus the 'reasuringly expensive' english made piston without the lubrication slot in the back skirt (Presumably there must have been a reason RE specified a slotted skirt?)

Are there any views on the reletive merits of the two pistons? The Brit one sure looks a bit stronger than the 'European' where the top is only half attached to the bottom, but I know nothing of these matters!

[Tim NZ]

DONT go for the OEM T-slot split-skirt piston! All you are doing is refitting a known time bomb!
If you plan on riding the bike opt for the Forged version every time.
If you have no other option but to use the OEM style piston ensure that the top land diameter is NO LESS than 0.028" smaller than the nominal bore size (reduce top land diameter); when skirt clearance is too great and the top-land too large the piston 'slaps' and it accelerates oil ring breaking and piston fracture through the T slot.


Evidence of piston slap is a clear spot in the carbon coating around the top land, front and rear.