Starting Problems.

[B.Lewis]

Yep, given all this information (rebuilt in 1992!) my suspicions are focused on the crankshaft oil seals.
Still, the Ariel engine unit is lot easier to dismantle than many others - just make sure your seals are genuinely new, not old stock.
Unless anyone else knows different?

[johnwalsh]

Egg sucking time, do make sure the seals are the right way round too.

[fgething]

Hi Keith, thanks for your message, lots of good advise / reasoning, Your right i think, next few days should make decision on stripping motor and changing seals, thanks again, Fred.

Thanks John and Brian, will get help in choosing seals, regards Fred.

Only thing about the seals is that i thought worn seals would give poor starting Hot or Cold engine, yet my bike starts first kick from cold.

[B.Lewis]

I know!
Dodgy seals usually adversely affect cold starting.

My personal favourite suspicion is still that the coils are failing when hot, or maybe overheating while parked up?
Surely this would be a common fault on Leaders of there was a problem with the installation / cooling design?

Can you try replacing at least one coil?

[Roger James]

Hello Fred,
I've been following the posts regarding the hot starting problem with the most likely possible causes covered unfortunately because you cannot say exactly what work has been carried out on the engine and what parts have been fitted during the rebuild its difficult to offer positive advice, that said having experienced hot starting problems myself on a 1960 Arrow after an engine rebuild I just persevered with running it and putting on the miles and the problem went away without making any changes.
On another Arrow that's had porting work carried out on the crankcase and barrel inlet ports by person unknown it was a good starter cold but impossible to start hot and no amount of changes to parts or set up made any difference so I gave up on it and stripped it down, the same running parts but with new centre seals/bearing fitted were used on anther crankcase and there were no hot starting problems. .
I'm aware of others that have given up on engines due to hot starting problems and someone else who experienced a number of seizures on their tuned motor that no amount of changes or tweaks resolved has been put down to the crankcases being porous that I think is a bigger problem than generally known so keep that in mind if you fail to resolve the hot starting problem.
So were would I start if I had your problem, well I would change the Amal Carb first, I know you have mentioned in your opening post that you purchased a new carb, did you mean new old stock or just another carb, those Amals can be a bit temperamental especially when hot so try another preferably one off a running engine that was not having hot starting problems and see if it resolves the problem on your engine. I presume you have the correct heat spacer fitted between crankcase and carb, an original item is best, there are some awful reproductions about.
I know of other owners who have experienced hot starting problems and fitted a Mikuni carb and then had no hot starting problems from the outset of using a Mikuni, as you are probably aware it is a common practice these days to fit a Mikuni carb although I've not gone down that route myself on any of my bikes sticking to Amal carbs but have been thinking about fitting Mikuni after paying for a Amal carb to be reconditioned, bored and slide sleeved did not work properly but I dont know why.
If fitting another good carb doesn't solve the problem then I would remove heads and barrels and inspect everything closely, are the bores highly glazed? if so give them a light hone, this solved starting problems on one of my Leader engines, but that one wouldnt start cold until bores honed.
Have a look at the inlet ports, are they standard or have they been opened up, perhaps too deeply affecting inlet timing leading to too much fuel mix entering the engine crankcase resulting in too much fuel mix in crankcase for hot starting.
If you are happy with barrels, pistons, rings and bores and after reassembly the hot starting problem persists then at that stage I would be considering an engine strip down to have a look at the crankshaft journals and change the seals and bearings, they've been in your engine a long time now.
Regarding Seals, Do not use new old stock seals, I've been caught out recently using new old stock that soon failed in use cracking and hardening although that might possibly also be down to the content of fuel we have to use these days so I would also advise you to forget about the black coloured Nitrile seals even if new and fit the much better Viton seals that most of us fit these days, they are a a Reddish brown in colour, I get them from my local bearing supplier without any problems, they are nothing special in Seal World and are no more expensive than Nitrile seals. You cannot get a single double lipped Viton seal for the centre of the crankscase so as Ariel did in the early days of production fit 2 seals back to back they are much easier to remove also than the single double lipped metal caged seal but a little harder to fit and get them pushed in fully home in the recess of the crankcase, make sure the offside seal doesnt stick out a bit that can end up rubbing on the crank web.
I thank that's enough for now, good luck. Roger

[fgething]

Hi Roger, thank you for the compressive reply, theres a lot to think about and it's going to be interesting trying to find the solution to my problem. As i said earlier i bought a new Carb from Amal, it made a difference to the starting and running from the original even though i renewed the jets and needle in the old one before buying the new. Going to try the new coils when the weather picks up a bit, will report back on any changes, thanks again for your help. regards Fred.

[grahamhibbs]

Roger, can you give me the part numbers for the Viton seals.
Regards.
Graham.

[Roger James]

Hello Graham,
Taken from the Bearing Suppliers packaging the reference numbers for the Viton seals are as follows.
Centre seal 21213737R23 Viton
Ends seal 17510025R23 Viton

Attachment pictures taken during the fitting of Viton seals, back to back in the centre of the Arrow crankcase.
Roger

[grahamhibbs]

Roger, Thanks very much, I'm going to bite the bullet and change mine.
Graham

[B.Lewis]

Roger's detailed and comprehensive reply is exemplary.
I'm glad he confirms my warinesss of NOS seals.

But surely it will be be easier and cheaper to change at least one coil FIRST before a thorough engine strip?

Maybe like these?
http://www.ebay.co.uk/itm/ARIEL-ARROW-L ... SwiYFXHlbn