Which pistons

[DerekElliott]

I am thinking of fitting new Pistons and a rebore, having run my engine for a while there is a rattle more like a tinkle coming from the cylinders at first i thought a washer or something had fallen into the cylinders but no, I have stripped the engine had the crank out but nothing untoward is in there. Dragonfly do a Suzuki piston kit including small end bushes has anyone used this kit and can recommend it or should I go to ebay where there is an array of Pistons available can anyone point me in the right direction
Regards Derek

[Roger James]

Hi Derek,
Although it can be somewhat annoying to hear a tinkle or 'Piston slap' on Leader/Arrow engines as long as its not excessive then its not a bad thing because you've got piston to bore clearance and there will be less chance of it nipping up or an outright seizure. Its certainly not uncommon to get these noises when starting the engine up cold and it will disappear or at least lessen when the engine warms up (as piston expands). If you cannot live with the noise of piston slap then have a rebore done and fit new pistons when it should run quietly but I doubt it will remain quiet for too long before you get piston slap again, obviously it depends a lot on how much you use the bike and how you ride it to bring on the wear and to some extent what clearance as been given in the bore during the rebore process .
Regarding pistons, you could source some new Ariel/Hepolite pistons that would be a straight swap ie you wouldn't have to change the little end bushes but its getting harder to source original new old stock pistons these days especially if you want a particular oversize pair of pistons.
The common alternative these days is to fit Suzuki GT250 X7 pistons and these are probably what Draganfly are selling as they are more readily available in various oversizes but if fitting these then you will have to purchase and fit a pair of little end bushes as the gudgeon pins on Suzuki pistons is of a smaller diameter, but once you've fitted the little end bushes you will then need to reamer them out to size so that the pins are a nice sliding fit so they too don't nip up. The ring pins in the grooves of the Suzuki pistons are in a different location to those on Ariel pistons but don't worry about that as the gaps run clear of any porting. Another thing to make you aware of is that the Suzuki piston is slightly shorter in length from the pin to the crown that means at Top dead centre it doesn't come as far up the bore as the Ariel piston so you lose a bit of compression but that said for a road bike I don't think you will notice this, I've run Suzuki X7 pistons and have not noticed a loss of performance.
I will mention that you can have the top face of the barrels skimmed to restore full compression as I've also had done for a few engines but as mentioned for a road bike I doubt you would want to have that done especially as you couldn't go back to using the barrels for use with Ariel pistons.
A comforting thing about using at least genuine Suzuki X7 pistons from what I've been told is that they are made of a better quality material and a lower expansion rate than the alloy used in Ariel/Hepolite pistons but having said that a lot of Suzuki piston kits being sold now are reproduction pistons not made in Japan so that might not apply.
Finally regarding noises from your engine, you might be hearing noises from worn little end bushes sometimes described as a tinkle or just plain resonance from the cylinder heads, not much you can do about the latter other than fit suitable small rubber blocks between the fins as some owners do.
Hope the above helps. Roger

[DerekElliott]

Thanks again for response Rodger very helpful
Your diagnoses of my problem seems to be spot on piston slap and resonance from the heads and piston sounds logical it's the same tinkle when you tap the heads with a spanner.
I have two spare Pistons plus 20 thou the ones on my previous thread and std barrels which I am using at the moment,my idea is to bore the std barrels to suit my oversize piston the clearance I calculate is plus 2-4 thou considering the manual States check the clearance with feelers 2 to 3.5 thou I am able to bore the cylinders myself then hone to the size.
I have spent a lot of time restoring this bike and i want the engine to sound and go as good as the bike looks, I have a recipt for the engine rebuilt by the previous owner which cost over £500 back in 2007 there are the problem with the seals and bearing didn't sound too good, the Pistons are odd one says Ariel the other I assume are Hepolite but they don't look the same, clearance in the bore is 6 thou, the crank reconditioned and looks good no wear at all
So two of us have been ripped off I paid over the odds for the bike considering the engine should be up to scratch.
I will always remember and visit to Caldwell park classic bike race, in the pits was a arrow
Speaking to the owner said the Pistons they fit when you buy a new bike are as if they worn out too much clearance he fitted Suzuki Pistons he advised me to stay for the last race the all comers which I did he came second beating Goldies Nortons and many other bigger engine bikes this probably wasn't only due to the Pistons but many other mods and his riding but it was very impressive to watch
Thanks again for your advice, by the way are you attending the Classic bike show at Stafford this year I go every year normally on the BSA stand
Regards Derek

[Roger James]

XNR at Cadwell September 2014

Hi Derek,
Its good that you will be able to do the rebore yourself, you'll be able to get the clearance spot on.
Regarding different pistons, there are the all Alloy type fitted by Ariel then there are Hepolite Pistons that tend to have, I think 'Brass inserts' for the gudgeon pins then I've seen Alcan pistons but to be honest I don't know whether Ariel made there own pistons or they were all made by Hepolite for Ariel.
Some pistons have just one hole each side on the inside to help lubricate the pin and little end bush whereas some pistons have two holes each side supposedly in recognition that the little end bushes can suffer from not getting the lubrication that they should get and need.
Over the years some of us and that definitely includes myself have experienced problems with the All Alloy pistons from the gudgeon pin wearing the holes oval prematurely, you end up with what we have termed, Death Rattle mainly heard when you switch the engine off and its in the process of slowing down the pin starts hitting the top and bottom of the worn hole causing a distinctive rattle, we think that is why the pistons were brought out with the Brass inserts for the gudgeon pins. There is a census of opinion that the all alloy pistons are o.k. to use with the low compression heads but best to fit pistons with the brass inserts when using high compression heads.
The all alloy Suzuki x7 pistons appear to stand up to the stresses better when used with high compression heads probably the better quality alloy they are made from.
I mention this incase your plus 20 thou pistons are all alloy type and you will have high compression heads fitted.
Interesting your chat with the Arrow racer owner at Cadwell, can you remember who it was?
I ran two Arrows at Cadwell last September, just Parade Riding with B.H.R. not racing, but I still enjoy myself.
I will indeed be at Stafford Show all weekend with one of the Arrows on display with the Leader & Arrow Club, there are usually about 10 Leaders and Arrows on display, the stand is in the Main Hall up on the balcony.
I'll see if I can catch you on the BSA stand. Roger

[DerekElliott]

Hello Rodger
The Pistons I am planning to use are Hepolite and have the bronze bushes fitted they are used but look fairy good I can go down the route fitting x7 Pistons but the main problem is reaming I do have a reamer that I can use but if it's slightly out out square they are no good so I will try the piston I have and hope for the best
The racer at Cadwell I don't know his name but he really made that arrow fly
I am going to the Stafford show on the Saturday but this time I won't be on the BSA stand,I am looking forward to seeing your stand and the Ariel bikes.
All the best Derek