valve springs too strong?

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Brian Petheram
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valve springs too strong?

Postby Brian Petheram » Tue Jul 09, 2019 4:03 pm

I am fitting the rocker covers on to my 1939 VH Red Hunter rebuild and I am wondering if the valve springs I have are too strong (there are a few references to this in previous threads I turned up by doing a search). When both the rocker covers are tightened down it is very difficult to turn the engine over and the exhaust valve lifter doesn't have enough force to move the valve. At first I thought that the push rods were not seated properly and binding on the covers but I've had the rocker boxes off 4 or 5 times and carefully lowered them using the long bolt as a guide according to the instruction book. The rockers do move up and down evenly and the tappet clearances can be set OK.

I have 4 other bikes with an exhaust valve lifter and they don't need anywhere near that much effort to work (although the VH does take the prize for puniest lever with least leverage). I can just barely turn it over using the back wheel in gear rather than the kickstart lever when the covers are tightened down. Admittedly it is up on the hydraulic bench so I am doing it by hand and can't bring any weight to bear but this is in a different league from any other bike I've encountered.

Are the springs really meant to be that strong or is there some error I could have made on assembly?

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alan.moore
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Re: valve springs too strong?

Postby alan.moore » Tue Jul 09, 2019 4:54 pm

Brian,
My '39 VH does not take any significant pressure on the decomp lever to operate the exhaust valve spring, a firm push with just the thumb is sufficient. The WNG is the same. I suspect your springs are too strong, where did you source them / any identification details

Cheers
Alan
1939 VH Redhunter;1942 RN WNG;1951 Triumph 6T Thunderbird;1970 BSA B175 Bantam;1986 Yamaha SRX600 single
http://cloggymoore.wix.com/triumph-pre-unit-6t

Brian Petheram
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Re: valve springs too strong?

Postby Brian Petheram » Tue Jul 09, 2019 5:22 pm

Hi Alan

thanks for the prompt reply - I got them from John Budgen about 4 weeks ago. They were supplied as correct for a VH - both the club and Drags were out of stock I believe.

Cheers
Brian

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alan.moore
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Re: valve springs too strong?

Postby alan.moore » Tue Jul 09, 2019 5:34 pm

Here's drags valve spring page link https://www.draganfly.co.uk/ariel/4-str ... es-springs there are a few different versions for the Vh depending on the year. The listing gives the free length which may help identify what you have.

How did the new ones compare in length etc to the old ones/
Cheers
Alan
1939 VH Redhunter;1942 RN WNG;1951 Triumph 6T Thunderbird;1970 BSA B175 Bantam;1986 Yamaha SRX600 single
http://cloggymoore.wix.com/triumph-pre-unit-6t

Brian Petheram
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Re: valve springs too strong?

Postby Brian Petheram » Tue Jul 09, 2019 6:24 pm

Hi Alan
I didn't have any old ones - the bike was not complete - and also I didn't measure them, just fitted them (along with new spring washers, collets and valve caps etc.). It was hard to tell the strength from fitting them as I have a big valve spring compressor with loads of leverage so they seemed normal then. I found quite a few mentions of VH springs being too strong on older threads when I did a search.
It may be that I can live with them as they are or perhaps there is a known alternative. It's just that any stiffness turning over an engine during a build has me concerned especially as the plug is out so there is no compression. The engine spins ok by hand with the kickstart if the rocker boxes are off but when one is on it is very hard and when both are on it's almost impossible. I worry that I may have done something stupid - wouldn't be the first time. I've rebuilt loads of bikes over the years but am new to Ariels.
cheers
Brian

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alan.moore
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Re: valve springs too strong?

Postby alan.moore » Tue Jul 09, 2019 6:39 pm

It should turn over pretty easy by turning the back wheel in fourth gear with the plug out. There is nothing odd about the Ariel valve train so if you have the cam timing correct (so you don't have a case of a slight clash between piston and a valve) and you have valve clearance on both valves at TDC then I would suspect the springs. If I had a spare set I would let you have them to try out but I haven't. I am sure someone on here will be able to lend you a set just to try out. I certainly wouldn't want to run it until you are happy the springs are not too strong.

Cheers
Alan
1939 VH Redhunter;1942 RN WNG;1951 Triumph 6T Thunderbird;1970 BSA B175 Bantam;1986 Yamaha SRX600 single
http://cloggymoore.wix.com/triumph-pre-unit-6t

Brian Petheram
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Re: valve springs too strong?

Postby Brian Petheram » Tue Jul 09, 2019 7:32 pm

I have tried turning the rear wheel in second gear with the plug out and it does go over with a lot of effort. I am a big bloke and find Panthers and Venoms easy to kick over. The valves go up and down as they should and the clearances can be set ok. I'm sure the cam is timed correctly. My main worry was a misplaced pushrod (I had that once on a Triumph Twin) but the valve lifter issue would not be affected by that so I'm fairly sure it's the spring strength. I'm happy to buy another set if someone can recommend some.
Cheers
Brian

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Re: valve springs too strong?

Postby Simon.Gardiner » Tue Jul 09, 2019 10:58 pm

The exhaust lifter can be very stiff if there's any notching in the lug it bears on in the end of the rocker lever.
I don't recall the valve springs being strong enough to make the engine difficult to turn over on the kick-start, although mine are strong enough to move the crank round to beyond where I'm trying to position it when I'm trying to do the tappets, without me putting the bike in gear.

SG
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)

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Re: valve springs too strong?

Postby nevhunter » Tue Jul 09, 2019 11:48 pm

I think I would change the springs. Have the tension checked if you wish to persist with them and the length at which they coil bind, which could be happening . Your cams will most likely wear excessively (common with strong springs) as well as the two gears in the drive . Use top gear to move your engine on the stand preferably. Nev

Brian Petheram
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Re: valve springs too strong?

Postby Brian Petheram » Thu Jul 11, 2019 11:41 am

Just to tie things up a bit, I have refitted the rocker boxes yet again and using 4th gear the engine turns over smoothly. I am amazed how much of a difference using 4th instead of 2nd makes - you live and learn! The valve lifter needs some attention as it did lift the valve a bit but then slipped on its taper so that's a separate issue.
I take the point about strong springs causing wear on cams and gears so will monitor the tappet clearances closely, however I will stick with these springs for the time being and see how things are when I am in a position to run the engine.
Thanks for all the advice.
Brian


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