My recently resurrected Maxini runs extremely well - as long as I don't open the throttle fully. When I do that it seems to 'starve' for juice - and wants to die.
Now I suppose it would probably be that the main jets are too small, but I know the carburation on these wonders is weird so I'd like to know if there is something else that it might be.
BTW Mine has a flapper which seems functional.
I recently swapped engines and may have mixed the carb-sets up between the two. The engine in the bike is an 11H and the other is a 16R. The carbs I have left over are 36mm (35.~) at the final part of the throat.
Would be grateful for any thought on the subject.
Cheers,
Mike
POSTSCRIPT; Am also wondering what the real differences are between the 11H motor and the 16R motor if anyone can shed light on them. Thanks.
Is your flapper vacuum operated or just lifted by the volume of air? If it isn't vacuum operated one of the tricks was to tape nickels to the flap to offer more resistance to the air. You should also check that your accelerator pump is working. See if you get a good squirt of fuel out of the nozzles when you twist the grip. The stream is supposed to be between the butterfly and the side of the carb so it doesn't hit anything. I always kind of thought that if the stream hit the butterfly it would assist with atomization, but never did mess with it.
Another possibility is the accelerator pump adjustment. I was having that problem with my original US '83 carbs and increased the stroke of the accelerator pump and it pretty much cleaned up the hesitation.
Thanks for the replies.
The accelerator pumps works and flapper worked when I appied suction to its line before fitting. I'll re-check the pump and alignment and check the flapper with the engine running today.
Cheers
AHA! The actuating rod for the flapper interferes with the airfilter I have! Same with both my airboxes. But I'm only checking with the one airfilter I have, which may not be the correct part for the bike. It was on one of the bikes when I got them.
I have a new air filter on the way from England so I won't muck around any more with the intake side until I have it fitted - assuming it doesn't interfere with the flapper.
Cheers.
Mike
lolol Now back together but one cyl cuts in and out erratically. lololol Might have fouled an HT lead with the heat shield or done something silly with the airbox mounting, but if it's not those (unlikely to be) then I'll first check the float levs with transparent hose and if they're OK I suppose I'll pull the carbs off for another service and pay special attention to the fuel flow through them.
Anyway, also polished the easily accesible parts of the engine's left side today, so along with the freshly hand-painted and rim-polished wheels she looks great - from the left lololol
Quote from: MikeScoot on April 24, 2020, 01:35:08 AM
one cyl cuts in and out erratically.
If not electrical, then check your carb sync before you go ripping the carbs apart again.
There were 2 different air filters for the Vision. The first one was rectangular and was for use with the air controlled flapper. When they updated to the vacuum controlled flapper it took a different air filter that had odd shaped cutout for the vacuum diaphragm and rod mechanism. I am betting you have the first gen air filter.
You're right. Thanks! It's the wrong one for my set-up. And the new one I have coming is the same @#$%*%#.
Might have to remove the actuator setup from my box and look for details of the later set-up.
In the meantime have swapped coils and fixed sloppy HT connections but the same problem persists. Next would be ignitor but the one on my parts bike has some of the most woefully hacked wiring I've ever seen, going into a non-standard unit. Might have to try it anyway.
The only other thing I can think of is that there is a bit of material floating around under a jet in the rear carb. somewhere.
Off to look at that dodgy igniter.
If you have the vacuum actuator you have the later improved setup. You will want to keep that and find the air filter for that setup. Good luck on finding you miss.
I used a Fram CA3903 air filter and cut a 1/8th inch thick piece of abs plastic as the base. I bonded the filter rubber seal to the plastic with a silicon gasket sealer. I bonded two strips of foam on the top of the filter so the airbox cover holds the filter down. The Fram filter is small enough that it will not interfere with the actuator rod.
I think you can get a Unifilter that fits but the OEM is no longer available. I don't care for foam air filters so I did not go the Unifilter route.
Quote from: kevin g on April 25, 2020, 11:13:26 AM
I don't care for foam air filters so I did not go the Unifilter route.
I don't mind the UNI, have them on both bikes. They are a bit messy, and I think they pass more induction noise than with paper. Don't really know how good they are, but they sure do trap a lot of pollen
Well, I pulled the carbs down, paying particular attention to the rear one, and found a bit of cr@p at the bottom of the bowl. Thoroughly cleaned everything and then the bike ran fine with no stuttering with fuel provided by a testing bottle. While testing without tank or airbox I incidentally found a wee fracture in the top coolant line where it meets the 'T' piece. Easy fix on that - just cut about an inch off the line and refitted.
Later after putting the airbox and tank back on the problem returned. I can only deduce that the problem is likely caused by one or more of the following:
1) cr@p from the petcock/filter assembly
2) cr@p from fuel splitter line between fuel pump and carbs, which wasn't inspected internally (unlikely)
3) sneaky cr@p still hiding in the rear carb (unlikely)
4) dodgy HT cable to rear carb upset by being moved to get access to airbox to carb screws (unlikely)
Despite the ongoing minor problem I'm pretty happy. I'll action measures to rule out all four of the abovementioned suspects.
But right now it's Beer O'Clock!
Cheers :-)
IMO the stories of crap in the carbs are greatly exaggerated.
Fuel level in the tank affects the pressure, so it does make a difference. One tends to hold the fuel level higher on a pony tank than in the bike tank.
Try again with your pony tank. If it starts working properly again, then look at your fuel pump and float heights. Also try a full tank of fuel rather than just a few litres.
I'll try that but if it were fuel pressure wouldn't itt affect both cylinders and not just the rear one?
I'm thinking that perhaps I need to have another look at the emulsion tube.
Yes, but more pressure can tip them from good to not good. My bet is that you still haven't synced the carbs either.
Well I have checked the rear emulsion tube properly now (and punched and cut a new gasket), but alas, I found no offending shjt in there.
So now my attention will be on fuel pressure - as you suggest. I will also dig my vacuum gauges out and synch. the carbs.
Other than those things, I think the only possible other offender could be the ignitor, but I think that is unlikely to be the culprit.
Incidentally, the emulsion tube removal was a lot easier than I had expected. I simply ground the side of a nice pair of medium-sized side-cutters slightly to ensure they were very flush with the carb. body, gently gripped the tube and carefully levered it out.
Might pull the fuel pump apart after dinner, while enjoying the dialogue of the 1930 movie "Fighting Caravans".
Wow, Fighting Caravans - I had to look that one up. A Zane Gray book committed to celluloid and starring Mr. Cooper. Sounds like a classic.
I haven't been following your build so my suggestions may have been covered already. Before pulling the pump apart did you confirm the fuel level in both carbs is where it belongs? POD mentioned fuel level but I didn't see if you confirmed this.
Regardless how clean what you can see is, it's what you can't see that often fouls things up. Ultrasonic cleaners seem to work well for what it's worth.
I see you swapped motors - did you verify both cylinders build similar compression and at the same rate?
Final question - you mentioned running on a pony tank with no issues. Were you able to ride the bike with that temporary tank or was that running on the bench with no load?
Oops, final question part 2 - did you check for vacuum leaks especially around the throttle shaft area?
These carbs can be finicky but very rewarding when you get them sorted.
Hi Rikugun,
Yeah, that movie is quite excellent. Have read most of Gray's books and thoroughly enjoyed all of them. I lived in Japan for a very long time and each day befor leaving my school for lunch I would print the latest news to read after my meal. One day my printer was out of ink so I went to the small library I put together for my students. There wasn't anything interesting that I hadn't already read. But there was a beaten-up old cowboy book I had picked-up in a bundle I had bought from a used shop. I thoroughly enjoyed it, and then read almost all his books in quick succession. I couldn't stop!
Do you know he was the world's first writer to become a millionaire from his work?
lolol Back to bike business;
Yes, I check the float level (externally using tube) after every fuel sys. change.
Both cyls. have the same comp., but not sure about the rate.
No, I just ran on bench with no load. But did ride it with the tank and it went well for a while. So, I have added a new fuel cap to be bought as the breather on this one could be bad.
So next, I will check for fuel flow and pressure (if I can) with the tank on, and cap both tight and loose.
Cheers,
Mike
Thanks for the update Mike and continued luck with the diagnosis.
Thanks.
Didn't get a chance to do anything related to the bike today. Started work's morning shift at 06:30 after that put down a fresh batch of beer. Then it was time to cook first step of meals for the next 10 days, followed by various houseworks, late lunch, wasting time on the internets, and then back to work for the arvo shift. Then after that shift it was time to do the final steps on the meals. Just finished and it's 18:30.
Tomorrow it is work as usual then a run to the dump and a spot of shopping.
THEN NOTHING WILL GET BETWEEN ME AND MORE WORK ON THE BIKE! :-) :-) :-)
It seems I had/have a t least a couple of issues with the carburetion.
* The non-venting cap. It now vents. I drilled it, gave it a nipple and attached a moto-crosser type breather line.
* Very small amounts of unknown thick, sticky transparent liquid were hiding in rear carb body passages - notably
affecting main circuit and pilot function. Hopefully all are now removed.
All in all a pretty good day 'cos it was great to have the motor running the way it should - even though it now seems to flood easily and needs a rest before restarting. Will recheck fuel pump and regulator as function may be inconsistent.
Will also carefully check float valve function again in case pressurised fuel is sneaking through.
Oh? Is that the time? Beer o'clock! Yay!
After cleaning out both carbs again (no crap found this time) and carefully checking all innards of the fuel pump and fuel regulator, the motor ran fine for quite a while and then slowly died and couldn't be restarted until it had cooled.
The good news is that I have a new suspect! The vacuum line from the manifold to the fuel pump. I think that perhaps the line was not sturdy enough and may have been collapsing when it became hot. Didn't test to see because the carbs were off the bike when that suspicion occurred to me. Have replaced that line with a much sturdier one. Also took the opportunity to buy caps for the YICS nipples instead of the line I had connecting the two, which was interfering very slightly with the throttle sync. rod. and very difficult to route due to its sturdiness.
Will test tomorrow after work.
When it died did you think to drain the carbs to see what if anything came out? If the carbs had fuel in them, it may be ignition as the symptoms support that theory - runs OK cold and fails when hot. Then again, if this is a new symptom that just appeared after touching the pump and regulator......
Yes, it IS quite possibly the ignition.
Ran quite well for a good fifteen minutes this morning, then died off again. This time it restarted almost immediately without too much difficulty. Went through this a couple of times.
I have been running it with transparent bleed lines so that I can constantly check float level - but not today. Drats!
I did notice that it does seem to die in bot pots at pretty much the same time. So yes, it could indicate an ignitor problem.
Next will be a more thorough check of the petcock and if that looks good then things will be pointing more toward the ignitor. Has anyone ever had one apart? I had a quick look the other day and it seemed to be flooded in with resin.
Cheers
Don't want to sound like a broken parrot, but check your carb sync else you are chasing your tail.
Been done. No considerable difference.