another jetproblem

[chris.vredenbregt]

Hello ariel riders I have been following the jet discussion for the VB in another topic with interest.
I have a similar problem with my 1930 OHV G special.
When I start the bike ,which is easy most of the times, it stays spitting back when reving, even with the choke fully closed.
When the bike is warm, mostly after a mile the spitting stops and it runs good, but I am missing the end-shot( it should do 85 miles ) but 65 miles is the most.
I have a AMAL 29 (similar to 89) with a 1 1/8 hole in it, and on the moment a 180 mainjet, needle 3th position from top
The slide-cutaway is 6/4 and in good refurbished condtion.
I think trying out bigger jets ,one at a step, would be an option but I do not have them on a shelf and they cost 5 pounds each in holland so finding the right one could set me back 6x5 is 30 pounds after 6 attempts and leaves me 5 not useable jets.
Is there anybody out there with a similar bike who can tell me what jet to use 200,220,240 or even bigger?
I am not really intending to go cruising on 85(65 is scary enough),but I could do without the spitting back.

[john.nash]

I do not know whether this carburettor is similar to later amal ones or not.

My wife's indian enfield got a nice new amal and it took me ages to get it right (sometimes it's easy and sometimes ages of messing with jets).
Her's would spit back something awful on revving and dropping back onto idle. It got a bit better when hot (and I mean after quite a few miles of running).
It required a richer slide, in the end, to cure this final issue.

When you are wide open, what happens if you start closing the choke slide (I assume it's lever mounted) which effectively reduces the air and richens the mixture ? Feel like it picks up or does it instantly start to "bog down/fade" ? If you're about right, in jet size, then it should "bog down" pretty quick.
In addition, if you have it wound open and you ease off then does it feel like it's picking up a bit?

This is how I do it but it's time consuming and, to be fair, it's subjective, not that accurate but usually good enough for old bikes.
You can go and pay for a dyno run but that will cost you far more than a fistful of jets BUT it will be accurate and save alot of arsing about up and down the road.

BTW, I swapped my new concentric off my other VH500 today (onto the vb/vh hybrid) and it's much better. It feels like it needs a slightly bigger main for wide open throttle. Might have to buy one.
I do have a dished piston in there, which one person tells me is rubbish and Peter kemp tells me he runs with no problems in his singles. Who do I believe ?

[tony.barnett]

This site has useful tuning advice for Amal carbs:-

http://www.hitchcocksmotorcycles.com/hi ... remonobloc

Sounds to me like its the slide cutaway than needs altering, not the main jet Chris. Spitting when you rev it could be a too big cutaway (if its from low to mid throttle) or the needle position needs changing (if its mid to high throttle). They all overlap though so its not that easy.

John - I had a dished piston in my 38 VH for a while - the bike ran fine with it but lacked the top end, running out around 60 mph. Other than that there were no real issues.

[john.nash]

John - I had a dished piston in my 38 VH for a while - the bike ran fine with it but lacked the top end, running out around 60 mph. Other than that there were no real issues.

That describes my bike, now I've sorted out the carb/jetting and cam.
um. new piston maybe... won't get a hepolite one though.

[tony.barnett]

Chris,

The only data I can find for 500s is post war bikes fitted with 289 (1 1/8") carbs. If its any use the settings are:-

Main jet 200
Needle Jet 106
Needle Position 3
Slide Cutaway 3

[chris.vredenbregt]

Thanks for all your replies boys, I think I will have to try it out, starting with the 200 jet and try to find another slide.
The weather here is not good yet for roadtesting,so it will have to wait for a week or two.
I will keep the forum informed about the results.
Cheers Chris

[chris.vredenbregt]

Hello Boys I altered the carb to the specs that Tony gave and indeed the spitting has disappeared and the first testride was promissing.
Hopefully in the next weeks there will be longer testrides and than I can come to the annual with it.
I haven't reached the 85 miles/h yet but it feels as if it is there,I am not sure if I will try it out
I am glad to have this forum cheers Chris.

[dave.owen]

Chris,
I would suggest a 200 for general use, a 220 is the size I run my Vh with a similar size carb.the 220 will deliver extra fuel to keep it cool

Dave :

[chris.vredenbregt]

Thanks Dave I will certainly try it out, with the 180 the engine was getting hot even gave me sparkplug problems when starting again( had to replace with anorher one)
I will let the forum know
Chris