Forum

[Leon Novello]

Some examples from Australia, none of them are mine.
[center]

[/center]

[Tim NZ]

Typically the 350 does not suffer from piston crown separation.


Skirt failure or Piston crown separation is not unique to RE but was an issue with ALL British bikes that used a T-Slot Split-skirt piston.


No one offers a modified OEM 500 piston...




H offer an excellent forged piston for the 500 #901204


Simply follow their fitting instructions, which may entail a light hone of the bore to achieve optimal (looser) running clearances. This is due to Forged piston have a higher thermal expansion rate compared to Cast piston.


OR


JP in Australia make a replacement Cast solid skirt piston for the 500 Bullet JP 0582. BUT it weighs +/-35gr more than the OEM piston and the bikes are inclined to vibrate more. Be aware that their piston is NOT intended for sustained high speed (racing) use. Ride long and hard @ +5000 rpm with too large a skirt clearance and the thrust face of the skirt has been known to fail. (see Leons pic)


(I spent a long time fettling the optimal running clearance of this piston for them)




Caution: JPs catalogue also list a High compression (7.25-1) piston for the 500. They dont! It is a typo that they have not corrected in over 12 years!!!




JP prefer to supply their pistons with a tight fit gudgeon pin, I prefer a loose slip fit, and frequently hone 0.0005" to accommodate a 'slip fit'.




It is possible for the average owner to reduce the OEM T slot split skirt piston top land dia. assuming that the bore and piston are not already excessively worn. (Max bore to btm of skirt clearance of 0.006" as measured 3/4" down from top of the bore)


You will need a clean, sharp, fine-cut file and a micrometer. The objective is to remove 0.002" - 0.003" (0.004"-0.006" total) equally from the front and rear of the pistons' Top land, over a distance or no more than 3/4" either side of the centre line.
A few licks with the file is all it takes...




Worn bore? Previously 'nipped' the piston? (scores on the thrust face) 2nd hand piston with tight ring grooves? All are factors that effect piston 'rock' at TDC (piston slap) and ring seal in the bore




The objective of reducing the OEM 500 piston top land dia is to negate any possibility of piston slap. Excessive Taper to the piston skirt (wear) or too large a Piston to Bore clearance will effect the out come.




Me? I check the OEM 500 piston for ring compaction every 10000km. Tight rings? I replace the piston.

[Alan R]

Hi BINARY------- in answer to your question "Why fit a forged Piston" you may have missed this that I posted earlier....}------------ -https://www.carsdirect.com/aftermarket- ... ed-pistons -----and in particular look at the heading}--Characteristics.....This youtube vid shows how they are made..... https://www.youtube.com/watch?v=29hWFXR ... wowI#t=162

[Tim NZ]

Leon:


Looking a bit closer at your pic, both of those failed JP pistons show signs of extreme heat through to the under side of the crown???


The black burnt oil deposits indicate incorrect ignition timing. Do you know if either piston had 'picked up' at all?


(seized)


Seizing and or extreme temps to the pistons kills the heat-treatment temper of the alloy and contributes to the skirt failing...

[Leon Novello]

Tim: I don`t remember who posted them, only that they were from Royal Enfield club members. The piston problem was so bad at one stage, a spare piston was carried by some on long rides (Central Australia) and changed at the roadside.
[center]



[/center]

[Alan R]

Didn't our friend NORM contribute to this in the past ??

[Leon Novello]

Alan: Yes, Norm had many problems, I think they were mainly with Electras . He has probably joined the Foreign Legion to try to forget about them.

[dave p]

Is it my imagination, or do I remember hearing that the very late iron barrel bullets were equipped with a superior Europian made piston?My 2009 model has done around 25000 miles, should I be worried?

[scotty]

Tim both the pistons are from my 500 1994 bullet, first one failed as my bike was private import home market bike with 279klm on clock so expected things to be ok, after this found it had a 90 main jet indian economy second piston went when big end failed other side of goulburn but managed to get back to blue mtns piston went in last klm. Oth pistons were indian std ones crap now run an 87mm accralite forged piston which requires crank rebalance to 63% small vibes 100 to 105 klm but ok after that ok to 140. When you see the workmanship in these pistons and the indian ones no comparison.

[Creaky45]

Dave P, Of course you should be worried. You ride an Enfield. Worrying is half the fun. Thanks for all your replies. It's good to see others with the same problem. I am going to try to post some photos when Leon shows me how of my latest failure and a previous 535 forged piston with a hole in which happened way back. Tuning and timing were ok when that one blew too. Why is it so?