A65 Lightning project......

[Guitarzanbikes]

Hi Dave, Happy New Year, only just logged on and seen this. The Mikuni has a fuel enrichment lever on the side, you push it down, this opens up "starting jets" as I understand it (its a hell of a long time since I fitted it!) and this gets it going. Its a brass lever attached to a plunger is best way to describe it, sticks out on the left of the carb if memory serves me correctly. I never had a problem once we'd tuned that Mikuni at Allens and she ran absolutely perfect with the jetting set up we finalized on so unless after I parted company with the old gel someone has messed with them I'd have expected her to start and run from that side of things. Best of luck, giz a shout if you think I can help you some mate, all the best Mark.

[geraldhattrick75]

Thanks for your suggestions folks... Unfortunately I couldn't find any Champion N4s' so I've ordered some N4Cs'.

Choke- wise Gb, there is a choke lever, which I thought ought to be pressed down for starting, and which you have now confirmed mate...


I've had an enlightening moment re the starting problem... The Boyer Bransden instructions state two settings: one for the camshaft turning clockwise the other for anti-clockwise.... Stupidly, I was looking at the intermediate gear, where the timing thingies sit- which turns anti-clockwise.... Er, the camshaft is driven in the opposite direction .... clockwise, so my timing was all to pot.

I am now getting a slightly more enthusiastic cough from t'engine on kick over... I'm sure that can be turned into a regular firing cycle with a bit more effort on my part. (78 with two titanium knees takes its toll when kicking a bike over...)

Incidentally, I did a compression test on both cylinders... Does 105 PSI sound about right?


I'll let you know how his progresses, particulary once I get it fired up.... (Ooh er missus...)


Again though, many thanks for your help.

[Guitarzanbikes]

Hi Dave, glad you are getting closer to getting the bike running. Yep I've used the wrong timing holes on the plate with a Boyer before too! Is the Boyer you are using the one that came with the bike or have you got a new one? Am not sure if they fail or go out of spec over time. When I had the bike I had a real annoying problem that was intermittent and left me stranded a couple of times, basically after a lot of checking (helps when your best mate at the time is an auto electrician!) something in the "black box" was breaking down and going "out of spec" and causing the timing to go all over the place. This was early/mid 90's the black box was replaced then but is now going to be over 25 years old if you are still using it. The coils in the points position were never changed then and I bought the whole Boyer unit 2nd hand in the early 80's so if you are using that part then there's a good chance its 40 years or more old. As for which way the cam turns I can't remember without looking, I'm just happy if its turning!

[Mike Farmer]

 

I guess that you have already thought of this but just in case.

Any lowish almost unnoiceable, battery voltage can be  radically disliked by the Boyer system.

I had a minor problem with my A50 similar to yours. Battery was on the way out tho most things still appeared ok. I put the charger on it and left it on whilst trying to start it. Fired up and ran just fine.

Just a thought.

Mike

[geraldhattrick75]

Right then, the lightning has a good spark and spot on timing (thank you Dave B and others) and still it refuses to start. (or even kick back- like my Venom loves to do...)

I therefore have to suspect that the Mikuni VM30- 565 (small block) carb, which doesn't really seem to be getting any fuel to the cylinders, is at fault.
(All jets have been removed and blown through, as has the carb body airways)

I've put the float at the correct level (according to 'Allens' (https://www.allensperformance.co.uk/) but they seem a bit vague about other things on the carb... Seems it was BSA looking at the options of using Mikuni back in 1965.

I have: removed the plugs, pressed down the choke lever and held my hand over the carb inlet while kicking it over to force fuel into the engine... without any success.

I have forced some sort of 'engine start' into the intake and directly into the spark plug hole..... Nowt, other than the occasonal farting back in the exhaust pipe.

I just seem to be going round in circles with this piece of sh---, er, beautifully engineered work of art.

So,
does anyone on this site run an A65 with a Mikuni VM30- 565?  And if so, can you suggest anything?.... Please.

Alternatively, I have a couple of used Amal 389/206 monoblocs.... Is it worth while trying to get the engine to work on one of them?

Or, if any of you can think of anything else that I might do to get this damn thing running. (telling me to stick it where the sun don't shine is not going to help.... Anything involving fire or explosives will be given serious consideration......)

I'm now going to lie down in a very dark room......


Sorry if I sound like a pathetic, broken, man,
Dave

For some reason I found myself looking up the word 'Recalcitrant'..... Maybe as a future name for my bike....... 

[DAVE BRADY]

Hi Dave,

I fitted a VM30 to my A65 back in about 2000.  I bought it from Allen's with their suggested jetting and it ran great from day one. I am not sure of the exact jetting but even if a bit out the bike should still run.   

One thing to remember is that with no tickler it is not easy to know if the float chamber is filling up.

From cold, I usually turn on the fuel and wait to give the fuel a chance to fill the chamber and get to a height so that the starter lever/jet can get the extra fuel through.  Then with very little throttle the engine should fire up and run with the starter lever being raised within about 30 seconds on a warm day.

It is possible that there is still a blockage in the primary/starting circuit.  Perhaps the rolling road starter may be a good idea as you can get the engine turning and open the throttle to use the needle/needle jet part of the carb.  Before that though, recheck that fuel is getting to the carb. 

Dave.

[geraldhattrick75]

Thanks Dave (I thought I might have offended you by not listening to what you were telling me, earlier- apologies if so).

I've borrowed the rolling road but need to return it by the weekend, and my mate who I was in contact with last week has got Covid, meaning that none of my mates will risk coming over to help me load  t'bike on t'roller.....

I'll see if I can get an extension on the loan.... 

Thanks for the suggestions.... It's exactly what I needed.

Re your mention of primary/ starting circuit, that is on the carb isn't it? (by the way Allen's don't appear to have any Mikuni VM30's in, so I'll get in contact with them tomorrow....)

I've also heard rumours about the plug caps needing to have a certain resistive value, mine are reading 5K ohm..... Does that mean anything to you?


Thanks again Dave,
Dave.
P.S. If I sound desperate it's 'cos I really am....
(never had a bike so bothersome....)

P.P.S. I'll get the carb off tomorrow and re-examine that primary circuit.....

[FirebladeDreamer]

5K ohms is a pretty standard resistive cap value.
What you don't want to have is a plug that has
an internal resistor as well as that will weaken
the spark quite a bit. But as long as you're seeing
a good spark with the plug out of the engine
then all should be well.

[geraldhattrick75]

Yes FD the spark looks real healthy.

I've had it jumping huge gaps.....  (I consider 1/4 of an inch huge... My missus doesn't though...)

[Guitarzanbikes]

Hi again Dave, sorry to read of your struggles with the old gel, now you know why the article done about her in British Bike mag was titled "Forked Lightning"! Honestly Alan the chap who wrote it couldn't believe why I was persevering so much with all the problems I was having! I think the fact none of them were actually terminal was why I always came back to it, that and the fact it was my mate's dad Syd's old bike and had a fearsome reputation here in Winsford during the 70's, I reckon I always wanted to recapture some of that old glory you know? Anyway if you can track down the magazine you can read some of the fun I had during my years with it, we need to get together and have a brew (or something stronger) because I think you are going to need it! Well done for sticking with it and keeping going mate, many a time I just threw it in to the back of the garage and used something else, strange thing is I was always drawn back to fixing it and having "one more go" to get her sorted, as you do! Try tracking down the article in the magazine (cover pic attached), its a laugh! All the very best with it mate, Mark 

[geraldhattrick75]

Thanks for that Mark, much appreciated mate. I'll try and PM you tomorrow....

Meantime, given that I'm happy with the spark and the timing, the problem has to be the carb so I'm sending it to Allens for a service and to see what they say about it.....

I've stripped and blown it through a few times now and I can't see what else I can do with it.

I sure as hell can't afford a new one (£248.00), and an Amal alternative comes in at as slightly more.


To be honest I think I'd sell the thing once it's working but, the the price they go for- and having spent £4k on it so far, I'd just be giving away all the work i've done over the last few years for nothing, and that's not happening.

I'll let you know how it goes.

Returning the, unused, rolling road tomorrow......

Dave.

[DAVE BRADY]

Hi,

Let us hope Allen's solve any carb. problem and the bike runs.  If the carb is shot (unlikely) then consider using a concentric as fitted to the the later Thunderbolts.  Specified at 28mm for the single carb. models it will serve you well and should run perfectly out of the box. 
If you live not too far away, I have a fairly worn carb. that you could try.  I live in North Lincs.

Dave.

[Spaceman]

Apologies for coming a bit late to this thread but I would like to offer a bit of personal experience I have had with a VM32 Mikuni I run on one of my bikes.

This carb was originally bought from Allen's and came with their standard jet set up for the bike which proved not to be that good. In particular, the main jet fitted was too large which had a detrimental effect on performance and like many other owners it was found to need a 10 smaller jet.

For owners of classic bikes running AMAL carbs, the cold starting device on the Mikuni can take some getting use to with a lot of owners using it in the same way as an AMAL choke. It is not a choke but an enrichment device which is either on or off!

I'm not sure whether the A65 will behave the same but, on my other bike, the thing you have to learn early on is that with the 'choke' on, after about 3 kicks, the engine will become flooded and will not start no matter how hard you kick it. At that point, the only way forward is to switch off the fuel and ignition and then kick over the bike 6 or so times to clear the flooding which, on my other bike, is made easier using the decompressor.

The Mikuni is a good carb for performance especially compared with an AMAL but is a bit thirsty in comparison. If the carb is operating correctly and the enricher is working properly, I would expect you to see wet plugs after you kick it over at the very least.

[idie]

If you have use of a rolling road use it you can at least open the throttle and get passed the idle jet and maybe get it to run. If you do whilst it is running put your hand over the carb intake and see if you can suck out whatever is in the jets.

[Guitarzanbikes]

This will make you laugh, maybe, during some of my worst times with the bike (early 80's) a horror film about a possessed car came out called "Christine", i was convinced I had the A65 equivalent, folk told me I was either mad or possessed to carry on! I have to say that on the two occasions I had buyers in my garage they walked away, can't say I blame em! You have to laugh Dave, it was all I could do at the time mate!