Which pistons are available for my ariel

[brenton.roy]

David, I have a used +30 Robbins for a VH.
I only have the JP in the bike, and threw the first one away in disgust!
I'll have a go at 250 Oven temp.
I will also try boiling in water for 15 minutes. Even though it is a lower temp, would this give a method that can be more accurately copied?
The results at different temps should be linear.
If you can get enough results, perhaps we could put together a table for the knowledgebase?
It would be useful to know the operating temperature of a hot motor. Any idea how this could be measured?
I would be very keen to see the results for a forged piston - ie wiseco - even if not for an Ariel.
One of the things we will not be measuring, which I think might be a problem, is whether the expansion is even.
I have pistons for other models - and will make up a list.

PS - anyone know anything about Robbins pistons?
Brenton

[brenton.roy]

Hi Harley experts. Will this wiseco 10:1 fit in my VH?
I can get 83.52mm as the closest fit via ebay here - Item number: 130631943202
So, I guess it would be available through Serco in Aus.
Will the dome work - or even fit in the combustion chamber?
Brenton

[nevhunter]

I've never used the high top ones in anything but the original bike. The Harley head is quite deep. I think there is too much dome for the Ariel. There is a lower compression piston available for the 1,000cc sportster and I have used them in the JAP KTOR Brough engine and they are perfect for that, so that is the one I would recommend.
venolia Arias and wiseco are all good pistons and the forged ones do not need the clearances they used to. The full skirt piston like the illustration cools better than a slipper type. ( More wall contact) Nev

[brenton.roy]

Ok, so here's where I'm up to with the VH. It's a '48

I've had the barrel measured and it's beyond repair. Getting the bore straight would ruin the sleeve that's in it.
So, new sleeve, shouldered so as not to slip.

I will give up on forged pistons for now. I wrote to Arias and Wiseco, but no response. I did find a price quote sheet for work done at Arias, so will follow this up for later. I'm reluctant to go against the advice of those (like Nev above) who know more re Harley etc pistons, so will settle for a 9:1 JP until I know more. As I have no transport costs, they aren't that expensive - AU $146.46 + tax.
The nice man at JP's was NOT happy that I wanted to use 10/8 thou clearance. Apparently this will void their warranty!
I did look into Nicasil (well, the modern equivalent) but it's AU $400 and I have varying reports about whether it works. Great in my Guzzi. Not so sure for a VH.

I've ordered the Franklin cam and have sent a blank and single lobe followers. This is their P1, of 1,2,3 where 3 is probably a standard R.H. grind. We'll see how that goes. David has been very happy with a P2 grind on his NH.

I've decided to have the flywheels dynamically balanced. I don't have the time right now to make up a pair of knife edges, but will put this on the "to do" list..
It's not horrendously expensive - $150 ish, and hopefully will only have to be done once.

I could do with some advice re the balance factor.

Reading "Tuning for Speed", I have the understanding that a higher number will move vibration into lower rev ranges. He talks about 66% as an upper number.
The way the bike behaves now is that it vibrates badly around 55 / 60 mph. I have been reluctant to go much faster in case it detonates. This would be fine (the vibration) in other situations, but not while motorcycling.. It's high frequency, itches through the kneepads vibration.
So, if you are reading this and have had your crank balanced to a particular number, please reply to this and let me know how it worked.
I'm aware that the other top end problems might be a cause of vibration, but given the motor is half apart, it seems wise to sort this now.
I'm not worried if it vibrates in lower rev ranges, as it will spend much of it's life out of the city.

Riding wise, I'd just like to be able to sit on 60mph comfortably and stretch it from time to time. I may be pleasantly surprised, but this would make me quite happy.

The rest of the motor is in more or less new condition. I've been running it fairly rich, out of fear that a lean mixture will make it hotter and exacerbate the seizes. So, the head needs a clean and it looks like there is a small leak at the spigot to tidy up. I'll progressively go leaner in mains when I'm confident about the top end.
Mains and big ends, bushes etc have only done a couple of thousand miles and look / feel like new.

I do need to clean the maggy - can you use the spray for electronics components? (not wd-40, the proper stuff) - or will this damage the windings?

Brenton

[ian.scott]

You need to settle on what pistons you are going to use and stick to that make as the different weights will influence the balancing you are getting done.

Ian

[nevhunter]

use the JP But don't use as much ovality as they say. Stick to .008" clearance . Use a balance factor of 66%for the single. I can't work out how you would dynamically balance the built up crank You would have to make a dummy weight and dismantle the B/E to fit it on. Your VH is a press fit and I don't like pulling them apart if not necessary. Having the wheels out of true will cause vibration. Nev

[brenton.roy]

Hi Nev. I will stick to the clearance.
I'm using Chris Milton, who has done a lot of racing motors, cars and bikes, here in SA.
They assure me they can do either static or dynamic balancing, given a piston assembly mass and a balance factor. I'll enquire further as to exactly how they will do the dynamic balance.
Given the $150 quote, I can't see that they would pull the crank apart.
I'll give them the 66.5% factor. Given the history of this motor, maybe 666 is better?
The flywheels were trued, but I guess they could have moved when it seized?
I've checked the small end for ovality, but it seems ok.
Ian, yes, you are right, but by the time I have sorted this, I'll have missed a summer of riding. I have most of a second motor. If I get lucky finding the parts, I will use this to experiment with.
I should be able to keep the current assembly as one unit.
Thank you both.
Brenton

[robin.parker]

Brenton, I'd be inclined to let Chris Milton have access to a proper (worn out/broken, whatever) OE Piston assembly, and a new JP one, ask him if he can work out the necessary Balance Factor changes. I'll bet my next month's pension that your VH's vibes at 55/60 mph (like mine) are all due to the terribly heavy JP. This VH piston business is a real pain, if you can overbore to 84mm, maybe the Vincent piston is an answer, I must pester Thorntons about those forged 83mm Ford/Lotus ones they were advertising. Or should we form a gang to raise enough money to have Omega make some for us? Goodness knows.
Best of luck,
Robin.

[nevhunter]

I would suggest if you have the time, spend it on lightening the JP piston as much as possible 66% is supposed to be the factor. Velo's and nortons use higher but most singles use 2/3 of the reciprocating weight, as a good start point.. I can't see how you can balance the assy with the rod there dynamically. IN any case if the flywheels are original and you take an even amount from each wheel and that will be ok. The drilling is usually done from the inside faces The lighter the piston and rod the better the vibration outcome .. Frame harmonics affect the factor which is best for various bikes.
The ariel single can be quite smooth, so it's worth trying to get it right. Nev

[brenton.roy]

Hi Robin, thanks, I will take a dead piston with me. I think I have an old low comp one somewhere.
Thanks Nev, yes I will try.
There was a lot of interest in this topic on the other Ariel group, and from memory, the weight of the pin was significant.
I'm going with a HS piston at least in part because I think this is made from a different blank.

If the club went into having pistons made, there would be a couple of issues.
1. They would be more expensive. While I'd be happy to pay more, I'm not sure how many others would?
2. They might need to be carried in two combusion shapes - High comp (HS etc.) and standard, plus oversizes.
3. If the pin weight is a significant issue, maybe these could be made available.
4. Other models?

Personally, for this to be worthwhile, I think they'd need to be forged.
Anyway, here's the link to Arias. It at least gives the details we'd need to make / enquire about an order. http://www.ariaspistons.com/custompistons.html
Also for Carillo http://www.cp-carrillo.com/Downloads/Cu ... fault.aspx - who also do rods.
I'm not sure where to from here at a club level?