Just a few words to let all the people who made comments on my 520 single back in May .After a long and difficult time trying to get this to run trying different carbs jetting timing etc ,there was a red herring.Conversations with Tony Harris we decided to put one of his carbs off his es4 still no good ,so a call to Mike pen it was decided he would have the bike to make checks which he did after 10 hours work Mike was puzzled.
In the end he rang tony back telling him what he had done there was nothing wrong with the settings on the engine,therefore there was only one thing left this was the new BTH mag .A telephone call to Tony could it be the mag very rare but could be.Tony had a spare mag which he very kindly sent to Mike to try and bingo the bike was transformed .i bought it back and took it out for a spin.My lord 45 in 1st 65in 2nd 80 in 3rd 95 in 4th.it cruises at 75 80. So there you go who would have thought a brand new BTH MAG would be the cause
Big thanks to Tony Harris (you are a star)and Mike penn without there help I would have slit my wrists .
i informed the company about this and they had the mag back and completely rebuilt it in front of my eyes,I fitted it and everything is perfecto
A nice end to a very long drawn out problem
Geoff Mcnulty
Hi Niel yes what a fiasco…
Hi Niel
yes what a fiasco I've had but anyway good now as you have read.
The answers to your questions first of all I have a model 50 350 bottom end with a alloy barrel bored out to 87mm this has a Yamaha piston in it the stroke is 88 so nigh on a square engine .The head is a 500 es2 with big valves and lightened rockers.The carb is a 34 mm Amal concentric mk2 with 280 main jet 30 pilot 106 needle jet needle position middle and a no 3 slide the engine has Castrol R in it.i think I have a 34 tooth engine sprocket which is Bob Newbey belt drive .The gearbox sprocket I think is 20 but not dead sure on the last 2 things.If it's something you really need to know I can have a proper look for you and let you know.
Regards
Geoff
Many thanks Geoff, the lig…
Many thanks Geoff, the light 350 fly wheel makes yours quite revy.
34T engine sprocket makes no sense though, even 24 would be pushing it.
My poor mans Manx on standard ES2 bore runs 20Tg/box and 22T engine sprocket, wouldn't like to raise the gearing any more.
Attachments pmm-pngPreviously Neil Wyatt wrot…
Previously Neil Wyatt wrote:
Many thanks Geoff, the light 350 fly wheel makes yours quite revy.
34T engine sprocket makes no sense though, even 24 would be pushing it.
My poor mans Manx on standard ES2 bore runs 20Tg/box and 22T engine sprocket, wouldn't like to raise the gearing any more.
Hi Neil, I think Geoff has got a belt primary drive, so the belt sprocket teeth will be much smaller than a chain which means the clutch is probably 64t or somewhere about there. The standard big-end bearingis not up to prolonged high engine speeds due to it's poor design, so keep an eye on it. Regards Richard.
Previously geoff_mcnulty w…
Previously geoff_mcnulty wrote:
Hi Niel
yes what a fiasco I've had but anyway good now as you have read.
The answers to your questions first of all I have a model 50 350 bottom end with a alloy barrel bored out to 87mm this has a Yamaha piston in it the stroke is 88 so nigh on a square engine .The head is a 500 es2 with big valves and lightened rockers.The carb is a 34 mm Amal concentric mk2 with 280 main jet 30 pilot 106 needle jet needle position middle and a no 3 slide the engine has Castrol R in it.i think I have a 34 tooth engine sprocket which is Bob Newbey belt drive .The gearbox sprocket I think is 20 but not dead sure on the last 2 things.If it's something you really need to know I can have a proper look for you and let you know.
Regards
Geoff
Hi Geoff
I'm very interested in what you have done to your model 50 engine as I've been toying with the idea of building one myself using a 1960 350 engine that's sat under the bench.
If you don't mind me asking, where can I get an alloy barrel and piston from and what sort of money are we talking about?
Are you using the standard 88mm crank and bigend and did you have to modify the crankcase and head to suit the big bore conversion?
Is there any vibration issues?
Regards
Jim
Hi Jim i have retained the…
Hi Jim
i have retained the 88mm crank and big end with a 6 1/2 conrod balanced with the piston at 70% .the barrel and piston were supplied by Mike pen but are not cheap at £600 .The crank cases had to be bored out to take the alloy barrel and head modified to take the oversized piston.
Mike pen does all this.He built the engine for me with race cams .The whole engine cost me the best part of 3 grand so not cheap but I am very pleased with what mike did as from the performance it's pretty quick and looks the business. The head was already modified for the downdraught inlet tracked.
Vibration is what you would expect from a single and is ok
If you need more info let me know
regards
geoff
Geoff, new magneto, who would have thought it?
So glad you posted to let us know what the issue was. I can't find your original thread, perhaps you couldn't either, so I can't find what carb and settings you settled on?
Your speeds seem good for a big bore single, I have a 530cc ES2 with a 20 tooth G/box sprocket but I'm sure an extra tooth on the engine sprocket will be better still in addition? I wonder what gearing you are running?