single mk 2 carb prob

have a mk 3 850 that I have fitted a single amal mk2 carb to and can't get the thing to start. the carb is brand new, jetted and with slides as set by RGM (who supplied it and have been good). The carb first flooded with petrol (poured out) so ckecked the float, the wire gauze to see if it was damaged and holding the float down etc. Now the carb is still flooding, ie the plugs are wet, as is the filter. is it a choke problem? how do I check? the bike ran ok on the mk1's but they were worn out and i wanted reliability (haha).

All settings start with the level of gas in the float bowl. Some of the really white floats that are new seem to not be too good. I like the two cycle part for this carb. Others say that the old stained yellow floats(4 cycle) work well for them. Because of the tilt of the body you may need to look after it. get the fuel level about 1/8 to 1/4 below the bowl top when running on the bike.
There comes with some of these carbs an alum. bushing underneath the behemoth that will drop right out. It enriches the low end circuit and is unnecessary. Keep a good eye on the enrichment circuit piston as it can drift to an enriched position on it's own.
The mark 2 will amaze you once sorted. I also like the two cycle brass slide that have a chrome finish. Lots of learning ahead. Nothings right right out of the box. All carbs need work to run your machine well.

mc

The sum of my experience regarding MK2 flooding centers on two issues.

Issue (1) If you have the Interstate tank, then the force/weight of the fuel on the float needle is greater. This results in the needle requiring more force to seat, so setting the needle seat height becomes more "touchy". It is less forgiving, and must be adjusted more precisely. Adjust by trial and error. I used a wooden dowel and pin punch. Tap the needle seat gently in or out. Keep track of the movements with calipers to find the "sweet spot". If you go too far, you'll suddenly stop/slow down on the highway until the bowl refills. Not far enough and it'll flood.

Issue (2) is like NORBSA says, the newer plastic used on the float seems to be less rigid compared to the older plastic. The problem is with the little tab that holds the needle. If you compare with the old, you'll notice that it is a bit more flexible. The tab bends too much preventing the needle from pressing down hard enough on the seat to create a good seal. This allows the needle to seep fuel past the seal and is especially aggravated if an Interstate tank is involved. Find an old style float on eBay.

My first experience with my new MK2 was the same as yours. I had flooding on start-up, and when the engine was stopped, there were several occasions when a continuous stream of fuel poured onto the pavement from the carb.

Another tip about the MK2, use the rubber flange type manifold rather than the round tube type. I believe Old Britts can supply this. It's a firmer fit that reduces vibration. To further reduce vibration, suspend the carb from a rubber O-ring attached to the frame. Get creative on this one.

Sorry for the bad news. Like you I was hoping for great things when I first installed the MK2. It's a fine carb when it's sorted properly and relieves you of the synch procedure when using two carbs. In addition it's an authentic Brit upgrade.

Gene

Gene1,
Some times the float bowl gasket catched the float and prevents it from working. Look at the two lugs on the gasket that go over the float hinge pin you may need to trim them.

Cash

Whilst the twin Amal concentrics on my 850 give good performance for some of the time they are for ever wearing and jamming on the slides. My previous bikes have all had Amals and I feel comfortable with them. Unfortunately the current manufacturing quality seems to be inconsistent. For example, one of my carbs became very galled and I bought a brand new body and chromed slide. Straight out of box the chromed slide would not enter the carb bore. I tried a new non-plated slide but this only entered the bore about an inch before becoming jammed solid.
I then had to emery the brand new carb body until the slides would fit! This took a considerable time but I did eventually achieve a lovely drop fit.
I trued up all carb flanges and fitted them carefully, having already set float heights. I carefully synchronised them and the bike went really well. Fantastic top end power etc.
Within 400 miles I could not get over half throttle. Both slides had galled again. I removed and fettled them both again and all was well - for another 800 miles. The throttle restricted itself again!
I repeated the overhaul for a third time and full performance was restored but only for 150 miles. Jammed again.
It is frustrating enough to be restricted to half throttle but what if they had jammed at full throttle?
I then made many enquiries about converting to single Amal Mk2 but after several phone calls to different suppliers in UK I concluded that I could not obtain my desired 36mm size with chromed brass slide. Supplies of this size of chromed slide have been nil for some time. So against all my normal instincts I fitted a single Mikuni 38mm from Allens Performance Parts.
This is probably the best change I have done to the bike so far. The Mikuni worked straight out of the box. Several optional jets are supplied with the kit but I found that a much smaller idle jet was needed to optimise idle mixture. The carb came with a 35 pilot fitted and a 32.5 pilot spare. Both of these are too rich. I am running a 25 pilot and it is brilliant. Throttle action is light and silky smooth and the off-idle and mid range torque is the best I have had with this engine. I rarely go much over 6000 rpm and honestly cannot detect any loss of power at all up to there. I am over the moon with the Mikuni. It starts first kick as well!
So, fellow Amal sufferers, I suspect that due to inferior quality control and the use of unstable mazac 'monkey metal' components it is mighty difficult to achieve satifactory consistent performance unless you are prepared to be forever truing and correcting manufacturing deficiencies in the modern Burlen-made Amals.

Cash, yes you're right there too, and the pivot pin can hang up as well.

No argument on the poor quality of the new AMALs. My first carb body was actually scrapped due to it being out of round. Liked to stick open but only happened when it heated up, well away from home. Got a new body and all worked well.

Another tip, I had a problem with the cable bend right at the top of the carb. Found a piece of stainless tube and fashioned the proper bend and all is well. I believe some Delortos come with the same style tube so it might be sourced as a part for the AMAL.

Got to thinking that maybe the original body was not the problem, sticking was due to the cable kink. Long story short I put it back on and sure enough it stuck open again. Makes for an exhilarating ride when you have only one RPM--5K.

Frankly, I have an original AMAL MK2, made by AMAL as my spare. If the current one so much as looks at me wrong, it's going into the trash bin and on will go the original AMAL. They are still available occasionally on eBay and are priced competitively with the Mikunis, I think. A much better built instrument than current production.

I use a K&N pancake filter and that fits well into the space left behind the carb. I think it may be the same one that comes with the Mikuni.

Gene

Gene1,
The gasket lugs catch on the float lug and prevent it from closing the valve.

scrim77
I'll bet the O ring grooves on the flages are'nt deep enough and when you nip then up the bodies distort. The force needed to squash the O ring is too high and the flanges buckle. The same thing can happen if you use a harder O ring.

Cash

checked everything yesterday, stripped the carb as i suspected a blockage somewhere. All ok so the float will be the next thing, it's a pain in the bum on a brand new carb though.
I am on the verge of giving up and getting a professional to look at it.
Sure I have been unlucky with this bike as it has been the most unreliable thing i have ever owned, and I have had a few Brits (BSA's and Enfields) and numerous Italian steeds (Guzzi's and Laverdas) not to metion Hardly Ablesons.
My wife calls it the money pit and I have ridden it once this year- it could be up for sale as soon as I have sorted it. (even had an electrical fault on the way home from buying it, an omen if ever there was one)!
I want my M21 back!

There comes with some of these carbs an alum. bushing underneath the behemoth that will drop right out

What is this? I know it is biblically unreliable, but I have no idea what the behemoth is?
Main jet? IE the biggest?

I will look at the gasket idea as a different float will have to be found somewhere. :?

First go here: http://www.hitchcocksmotorcycles.com/ than find Amal carbs and click on those, than click on: 28-34mm Amal Mk2 than look at item 13.
That is called: AIR INTAKE ADAPTOR not behemoth as I call it. Pop it off and if it's there you will see an alum. bushing it will drop out.

Cheers Norbsa, I'll check later today after work. I don't remember anything between the body of the carb and the air inlet but it's worth a punt!
Life was so boring with my Triumph 955! Although i did get more miles in on that one.
I'll report back.

Norbsa- I've taken to reading the posts on this forum without looking at the name of the person posting.

I'm getting pretty good at knowing when I'm reading YOUR posts.

hee hee

Hope you take it the right way.

Paul, It helps that we have met at the Castle de Carter's . Working along side someone is a good way to meet. Got to meet Lou who owns Relic Cycles in Texas, a big state I know but he has sent on a frame to me and I always like talking to others who toil constantly with old bikes. Lou and I met at the Norton National in Ohio Rally around the races.

I saw Luis on Sunday. Couldn't remember who it was that was asking if I knew him becasue the number posted on the BMOA site is wrong and they needed to talk to him.

Another one of those "man, I know your face, I just can't remember your name" deals.

Luis is a good guy.

The guys at RGM are sending a new float bowl,float,pin gasket etc from a running bike so I can compare and fit in place of the new one to see if I am missing something obvious. A couple of guys at a Trial bike event this week suggested I let RGM have a go before I start chopping things about or get another company involved,. RGM have been great on this so far. Will keep you posted.

Well, that's just too logical for the average situation!

mk 2 carb

thanks for all the help. RGM sent a new bottom end, float/bowl etc and it has stopped the flooding but I managed to break the earth lead (main) with removing the battery so many times and have fried the wiring!!!
The problem is that with riding modern bikes you forget what you need to be doing with the older ones, and I can't remember doing anything on a bike since I sold my last BSA 8 years ago. :cry: :x A new harness etc is on its way, but I am getting a professional to sort it out as the summer in England is only 2 minutes long and i'll miss it at this rate. It may be time to buy another bike to use as i have a feeling that this one is going to be a money pit (My better half's most printable name for it).
The tacho has been sent for repair after the i smashed it in a freak accident with an empty box.
Probably blow a valve next as everything other 'consumable is brand new now.

Harness and carb

Well the update is there is no update!
Can't get the local engine shop to do the work (guess there is more money in newer stuff) and the bike has sat in the garage for 8 weeks doing sweet f.a.
In this part of the world there is a scarcity of bike mechanics.
Lovely weather out there and I have done 6 mile on the thing this year.
I do have a week off next week and will attempt to put the new harness in but It is SO depressing! Tons of wires and connectors.
Anyone got access to a coulr wiring diagram as the haynes/Norton service books are black and white.
It could be a return to Hardly Ablesons at this rate as the whole experience has been gloomy.

Re: Harness and carb

mcmarvelous said:

Can't get the local engine shop to do the work (guess there is more money in newer stuff) and the bike has sat in the garage for 8 weeks doing sweet f.a.
In this part of the world there is a scarcity of bike mechanics.

Click to expand...

You are not that far (maybe 10 miles or so, - Braintree to Gt. Dunmow) from FD Motorcycles?: http://www.fdmotorcycles.co.uk/

mcmarvelous said:

Anyone got access to a coulr wiring diagram as the haynes/Norton service books are black and white.

Click to expand...

But they are marked up with the wiring colours, so I can't see there's much of a problem understanding which wires are which colours?

I have burnt out a main harness and replaced it with a new one, I stripped the bike to reveal the majority of the harness and loosely placed the new one in postion. I then disconnected the old harness 2 or 3 connections at a time from the front of the bike and immediately remade the connections with the new harness, I had a wiring diagram but only had to refer to it once or twice. I slowly made progess back down the bike and also every 12" pulled the old harness away from the bike and attached the new harness with cable ties. All connectors were smeared with dielectric grease which stops them corroding, at the end you have an old smelly harness in one had and the bike has the new one fitted.