Forum

[John Turner]

Jason, I have been running 612's for about 8 or 9 years and can well recommend the conversion. If you can rebuild the standard Bullet engine there is no reason why you can't build a 612. A little more care on the build is needed and the crankcases need a bit of machining for cam clearance. Do not be put of by the cams as these are advertised as fast road or race, the cams supplied with the kit are ideal for city work as well. The engine is well balanced and I would agree that vibration is possibly less than the std 500.
Bags of performance and mostly starts first kick. I think in the USA you have a lower octane of fuel, so a slightly lower compression may be more benefical by fitting an extra base gasket or thicker compression plate.
JT

[Roeland]

I´m running a converted 535 EFI and can only dream what the 612 will to to this bike when it becomes available. I all day long at 120kmph with pillion and camping gear. The standar EFI is limited to about 5250 to 5500 revs. I can rev my bike to 5800 and the torque is a dream - uphill; downhill.

[Midge]

Typical 500 piston failure, it seperates at the oil control ring area. When it happened to my '99 Bullet I rebuilt it with a standard piston although our hosts now offer a forged one. As to whether 'its worth it' to upgrade to a 612 is very subjective, depends what you want the bike to do. My personal view is that if I wanted more power and speed I would be getting a twin engined bike. I know that limits RE bikes, but there are others makes out there!

[Alan R]

Hi guys----------- and whilst you're releasing all that exra "Oooommpphhh!!" ABOVE the piston crown, don't forget it's still that same old ALUMINIUM con. rod slogging away UNDERNEATH !! (For the Classics that is )

[dave p]

Hi chaps.Those photo's look rather worrying!! Are these failures confined to the Indian made piston or does the later European made piston fitted as standard to the later Classic models suffer in the same way.Mine is a 2008 model with
30,000 kilometers on the clock.Should I be concerned?
Cheers,Dave P.

[Alan R]

Hi guys-----------yes, interesting photos, eh??---------Regarding the crown failing, there have been a few others recently--all showing a similar view...................LEON, are those the front or rear faces that have failed ??... To me they have the look of a metallurgy-based failure ie Both pistons have a normal, clean Aluminium colour with typical combustion-products seen on top...Cylinder wall boundary-lubrication would also appear to be functioning OK, there being no scoring etc.............. Now compare these with the other photo and the differences are quite clear.....First look at the colours... Signs maybe of overheating ?? Next are the two large patches of vertical score marks consistent with a boundary lubrication failure...Then there is the actual area of failure itself.. This is at either end of the gudgeon pin only and NOT the blackened area curving around...The whole CROWN has lifted vertically suggesting either an engine over-speed OR a metallurgy failure due to high temp. OR a combination of both..(Plus the stupid design in the first place !!).....Remember the OEM piston is CAST ALUMINIUM and the whole design ethos for these bikes was originally CHEAP,low-speed, pottering around........ To answer LOGS original question "Is it worth it ?"}------ I agree with MARK M and MIDGE, plus JOHN TURNER's de-compression plate to give better tractability...As you will now be doing a full engine re-build why not take the opportunity to fit a steel con-rod and thus have the COMPLETE engine upgraded and not just the top-half as I alluded to earlier on ?? ................... I hope this is not coming across as a lecture ??, but as an attempt to help .....PS, there's NO Octane in petrol as such---- it's a performance-comparison test done in the lab. in order to grade fuels and inform customers (OOpppsssssssssss, now THAT was a lecture-ette.... SORRY guys !!)

[Midge]

To clarify Daves question, the 'European' piston I bought from Mr H to replace the blown one on my '99 Bullet was exactly the same type. I still don't have an answer to why it happened, no prior signs or noises, lubrication in first class order, carburation ok etc. I had been on a run for about an hour in warm summer weather, I increased the speed a bit on a dual carriageway to avoid being pushed by trucks when at a genuine 55 to 60mph (sat nav) it decapitated. Leon's photo looks more like a 350 piston?

[Alan R]

Hi Guys-----------Hello MIDGE, whilst typing my post I was aware that it might come across as me blaming the rider so did try to put it in as "Neutral" a way as possible.....This is a long-standing problem with these OEM pistons... I've fitted a forged piston to my current bike as well as the 19t sprocket to help keep those revs down....Has anybody out there had a European-made replacement piston fail ???? I still think that the whole crown being attached to the skirt by just those two small areas is asking for trouble....Has anyone access to pistons from other contemporary 500 singles for comparison ( retro-fit, maybe ??)--------

[Alan R]

------------ just as a follow-up, what do our contemporary owners of BSA, NORTON, ARIEL, have to say about similar experiences I wonder ??.... Are there any parts that can be fitted eg pistons, con. rods etc ??? ...These questions have no doubt been asked many times before but it's always worth another go I think..... BW, have you done any cross-make mods ??

[Alan (Lancashire)]

Mr tollgate (tollgate classics) has used a fiat piston , and has used harley davidson pistons sucsessfully http://s236652202.websitehome.co.uk/500cctune.htm he made "the beast" a 666 cc bike , can,t find the review at the moment , 450 tollgate reviewed episode 6 of real classics