Thumper Club Forum
Technical => Bike Problems/Questions => Topic started by: andy230 on December 09, 2007, 08:15:29 PM
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I've measured valve lift as 0.478" on inlet and 0.447" in the exhaust.
I fancy springs and Ti retainers from kibblewhite:
http://www.blackdiamondvalves.com/
(if you're actually interested its part #80-80241) But you gotta download the catalogue, p119
This states:
.450” Valve Lift Ok
What do you think....?? I think I'll have to ask them. ie. is .450" the LIMIT? Or is it just OK?!
Dont wanna get coil-bound....
a
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Aye Andy,
That is the crux of this mate, max lift of cam versus coil binding compression limit of springs and your proposed springs will coil bind, spread and wear on their inner and outer surfaces ??? Don't even go there.
If you go here: http://www.megacyclecams.com/catalog/page60.pdf
Cam Number: 266-x4 is the nearest lift to the figures you have quoted.
You can see that the springs etc.required for this cam are Part Number: #120-Y valve spring and guide kit with titanium tops and capable of taking lift too 0.500".
I suspect this kit has guides which are shorter than standard, to allow the increased depression of the valves and the springs will be wound to a different length so as to prevent coil binding. ;D
Also note that this comes from a 2004 catalogue, so I don't know if they are still trading.
Finally, have you had a rake around in the Thumper Pages website if it is still going? I haven't had a chance to go for a rake about today! :)
Keep chipper, the $ to £ rate still isn't bad! ;D
Have a word with Joy Cams as well.
My regards, Bill.
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>:(
Hmmmm! Thats a shame.
Although it WOULD explain why the existing springs were worn on their inner and outer sufaces, wouldn't it?
I've got that page from the megacycle catalogue bill. Not much on there website, I think it will have to be a transatlantic phone call :o Hope they're still trading, else I'll have to get another cam :(
And re. the guides, the ones fitted are already shorter than standard, another reason not to change them.
And try googling "Joy Cams", or Joy Cam.... ;D Reminder, I work in a kids hospital!! :o Apparently phil joy is also a chef. I didn't find any site tho for Joy...
Will trwl the thumperpages
cheers for now. Anyone got any info on megacycle?
a
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And try googling "Joy Cams", or Joy Cam.... ;D Reminder, I work in a kids hospital!! :o Apparently phil joy is also a chef. I didn't find any site tho for Joy...
http://www.thumperclub.com/smf/index.php?topic=779.0
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Brilliant
I spoke to Phil Joy. He says MEgacycle are still in business, as far as he knows. No UK dealer, and they're a bit awkward to deal with apparently, but thats cool...
So we chatted. He reckoned 470-odd thou is VERY large opening.
I am going to go see him before I go up north.
We discussed the merits of opening one valve slightly before the other (ie. both inlets do NOT open simultaneously). Apparently better swirl, etc?
He has done a bit of work on this, and maybe it would be of interest...
Will let you know what happens. Thanks guys
a
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For Phil Joy look under this site's "recommended services"
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Aye Andy,
As the man says on the 'small port site' (U ken the one), "shovelling coal in is easy but keeping it in the grate to burn the stuff is the hard bit"! ;D
The swirl and the wee dimples all help to keep the petrol/air mix, mixed rather than dropping out in a laminar flow! Getting the mixture to swirl and fill the cylinder is the problem with old Dukes, get the port wrong and it just skites across the top of the cylinder and disappears out the exhaust. Naff! ???
If the weathers no bad maybe out for a run on 29th December if you're about, gi us a shout!
Enjoy the blether, I'd love to be a fly on the wall.
Regards, Bill.
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Aye Andy,
Another 'thought' about those guides! ???
The shorter they are, the less support they provide to the valve stem and the less heat transfer away from the valve they are able to disipate. ???
I've seen a shortened inlet guide in a Duke head, 'pick-up' on the valve stem and the whole lot come slack in the head. Messy! Same if the gas flowing is too enthusiastic and removes metal supporting the guide.
My regards, Bill.
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Granted Bill, but I think it was ok before...
But point taken, there's a pay-off... The guides *feel* ok..... I'll give it a bash.
Anyway, the stem seals will support! :D
Going for those RD springs, as per the Megacycle site. With Ti tops I think. Price is horrific.... But these are the only ones from a reputable manufacturer which can cope with up to half an inch lift. Its bloody massive!! Through this guy. He has been great for a bit of chat, advice, kicking ideas about. His ebgineering looks lovely too:
http://www.zabernet.de/bill/tuning.html
And I'm away down the road again oon the 27th, so a wee jaunt isn't on the cards sadly.
However, we WILL meet up at some point!!
Ca canny!
a
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Aye Andy,
Oh Satan behind me!
As for the meet, we'll see how we go. Your going to have your hands full all season and I could be busy!
My regards, Bill