1979 Triumph Bonneville 750cc, Swapping carburetors Part: 2 Amal Mk 2 Installation

[@spoerers]

I can't tell you how pleased I was to find this video. It's almost as if you had made it for me! I have a 1979 T140E with a slight but sometimes annoying hesitancy when opening the throttle quickly (when the engine is hot). Pilot air screw adjustment has not solved it. I've replaced the cold start plungers (to no avail) and the next step was to replace the jets and check that I have the right throttle slide cut out. Being able to refer to your video when re-assembling so will be so helpful! Many, many thanks.

[@jessesvintagegarage765]

If you are talking about the new plungers that are available, well there to long, and they leak air, so that's why we went to the cable operated choke plungers,

[@jessesvintagegarage765]

Oh and thanks for your nice comments, also let me know if you need more help thanks,

[@spoerers]

@@jessesvintagegarage765 do you mean the OEM plungers you can get direct from Burlen (owners of Amal)?

[@jessesvintagegarage765]

Yes the OEM ones from AMAL they are to long

[@spoerers]

@@jessesvintagegarage765 I had a discussion with Amal's tech support about the cold start plunger length thing. They said that the first design of Mk2 plunger could wear the area above the plunger's seat into a barrel shape, causing air leaks and rough running in higher mileage bikes. As a result they redesigned the plunger in 2011 to make the plunger's head longer, giving more support to the head end to keep the plunger from wobbling about in its bore, and thereby reducing the risk of that kind of wear. My bike has a relatively low mileage thank goodness. I've had a close look and can detect no uneven wear in my plunger bores. Given how the plunger works I'm not sure I understand why a slightly longer plunger head would cause a problem with air leaking past the plunger seat - the key thing is the quality of the seat and the closeness of the plunger fit in its bore. I don't see how a slightly longer plunger would affect that? The cable version is the same length anyway - perhaps you got some new old stock? Either way I reassembled and refitted my carbs watching your video and it was indeed of enormous help - thank you so much. Parallel inlet porting has made carb fitting a fair bit more awkward than the splayed inlets of the earlier models. I had spent some time wondering how best to synchronise Mk2s given the relative inaccessibility of the bell mouths caused by the parallel inlet design. It had never occurred to me to leave the float bowl and needle jets off and just observe the needles - inspired! Thank you again. BTW I plan to replace my float bowl screws with Allan screws to make the searching, slipping and sliding involved when screw-drivering the inner four and their rather awkward and inaccessible siting a bit easier.

[@billmago7991]

I've run twin mk11 s for twenty years......I like em, only thing is make sure you get the new stayup floats so you can adjust your float level,something you can't do with the old nylon floats. Also I ended up swapping the top cap with a metal one as the cable adjusters end up being pulled through the plastic threads

[@PR-lj9rt]

Hi guys. Thanks for the video!! Appreciate the time/effort you put into it. Any advice on where to find/purchase the stay-up floats? I've been looking for them online but can't seem to find any. Thanks again.

[@jessesvintagegarage765]

Thanks for the great comment, got a couple places you can check out, Bonnevilleshop.com AMAL part # 622/069A for $46.95 or Baxtercycle.com AMAL part # 622/069A for $45.00, Its called a stay up float upgrade kit

[@Goodtimesfilm1]

Thank you for a well described video. I have a 78 T140E that is all original and seems to be having carb problems. Mechanic is telling me to go with the 930 premiers but the bike originally came with the Mk2s. Trying to determine whether i should get a new pair of mk2s or switch to the 930s. any insight you might have on your experience with the 930s would be highly appreciated.

[@jessesvintagegarage765]

@@Goodtimesfilm1 Well that's an interesting subject I struggled with the same issue. The real problem is how original do you want to keep the bike? Switching to Amal Mk1's isn't just bolt them on and go. The cables are different and require a lot of mix and match because the 78 79 T140E has different twist grip and getting rear cables the right length was tough. But the bigger issue for me was mounting the carburetor flange to the round inlet spigots on the parallel inlet ports once I found something that could do that then the air cleaner connection was all wrong and had to find a way to connect the carburetors to the air box as it was important to me to keep the air box and side covers. But truthfully after all that the bike just didn't run as clean and smooth as it should have it always had a hesitation or slight stumble. So after that I started messing with the Mk2's again. In my case it was choke or enrichner plungers were worn out as starting was the biggest problem the other thing that really made those carbs work really well was putting 106 mk2 needle jets in and removing the stainless 105 jets every thing else stayed factory stock as far as jetting I did renew slides and floats. Good luck with your bike I hope this helped you.

[@Goodtimesfilm1]

@@jessesvintagegarage765 much help thank you! can i ask where you bought your needle and float from?

[@jessesvintagegarage765]

@ Amal mk2 parts are not always stocked by everyone so do some online shopping and you should be able to get everything you need fairly easy. Here’s the list of part numbers that I used everything else stayed the same, 2928/060 Number 3 anodized mk2 slide 622/149 viton tip float needle 622/069A stay up float these floats fit Mk1 and Mk2 carburetors some come with both types of bowl gaskets 2622/079 cold start plunger assembly 2928/122B Mk2 .106 needle jet it has a groove scribed on it and is different than Mk1 jet

[@Segsy59]

Nice tutorial, there's a number of permutations of jet sizes to choose from, it would of been good to see which you had. Nice one 👍.

[@jessesvintagegarage765]

Thanks for the comment, your correct there is all kinds of combinations to choose from but we used the stock US jet set.

[@jeffuren6942]

If the original bike year had Mk1 amals..DONT change to Mk2 amals...get the new redesigned .. Premium Mk1...has all the improvements you need including the material of the body is now Aluminium

[@everettskinner8195]

I am looking for someone to rebuild or restore my 1979 Bonneville special