This carb strip was carried out because the thing was hopelessly gummed up. As I haven't yet re-assembled the bike,I have yet to run it in any way other than a test firing. Consequently I don't know if this has effected a repair. This approach should be fine for a carb that is simply dirty or blocked- provided that there was no underlying problem. I should also add that tuning carburettors (especially in the light of today's modern fuel and oils) is something of a black art! I'd love to understand it but I don't. Look out for a future post detailing my attempts. However, I should add that Shane Woods (contact via fb group) can offer a carb rebuild and tune service and he has helpfully also penned a few comments relating to this account which I have reproduced after the blog.
The carburettor is located on the rhs. In this bike the choke button was jammed down and the throttle cable stuck firmly. It's held to the manifold by 2 nuts each fitted with 2 washers and easily removed. However, as I couldn't move the throttle slide I had to remove the carb with the cable attached. Detaching this from the throttle control showed that the cable was frayed internally and jammed in the throttle control.
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| Motor from rhs- jammed carburettor |
The carb top is held by 2 M4 cheese head screws. Once these are removed the top should be removable, but in my case the throttle slide was jammed internally would not come out. This carb was clearly doing nothing as it was jammed at both ends of the cable!
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| Carb top removed but stuck via the throttle slide. Note the fractured gasket that should be fitted below the cap. |
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| Choke slide removed |
Once the needle jet was out I could free the throttle slide by using a drift to tap it up from the bottom.
The main jet is accessible from the side as a small brass nut.
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| Float cap once removed. Note sealing ring around periphery of the cap. |
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| Throttle slide removed, view 1 |
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| Throttle slide removed, view 2 |
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| Base of throttle slide was pitted but hopefully this will have no effect on function. |
I placed all the components in the sonicating bath to clean and then brushed them clean. I sprayed all parts with carb cleaner ensuring that all jets and passages were free and then loosely reassembled the carb until I can get some new parts.
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| Carb type 1/12/136 |
New carb top gaskets are paper, and have been so for some time. The fragmentary remains I removed from the carb when I stripped it were rubber and this suggests it was probably the original. I'd like to have found a rubber one to replace it with, but just couldn't. In the end I cut a new gasket for the carb top from a sheet of nitrile rubber. I'm now informed that these gaskets never were rubber and although I've not had a problem with my home made inseret there are pitfalls (see comments at end of blog). When I stripped the carb I found the float bowl gasket to be a square section 23 26 O ring. I used a round section 1.5 mm thick O ring which worked well. Too thick an O ring here could raise the float height so again caveats in comments at end of the blog. The needle jet cover plug had a fibre washer and the main jet an O ring. Both were easily sourced.
So I've refitted the carb and tried to start the motor- this immediately revealed that I had no spark (see "Magneto"). However having sorted that, the motor did start but as I have no throttle cable at present its hard to be certain how well it runs! More later....
You did want feed back :) as I read your carb section and some of it is a bit wrong, eg the float bowl gasket was not square section it is round section but I see you fitted a round section anyway and the original O ring can be purchased if you know where or I can get them easily enough, rather than fit a too thick one as it can raise the float height if not done right, there are also various other areas that need attention on those carbs as they do tend to corrode and very soft metal but all can be sorted ok if you know what you are doing and also over tightening of certain areas can distort the parts and it can leak if not repaired or done properly, the top cap gasket should also be a thin paper gasket as its a measured distance and too thick a gasket will change the travel of the slide, there are various part changes for the carbs and some parts do fit but are not for some versions of Bing carbs for the Quicklys as there are many over the years from 8mm to 9 mm to 12mm, some with choke some without choke built in also, also there are the changes of fuel mix ratios with modern 2T oils and the modern fuel we now have to use that often need addressing as regards tuning of the carbs to compensate and even timing changes, as you may already know I fully restore the carbs for others, if you need help just ask , im on Facebook and in the NSU Quickly UK page where you can find me , Shane Woods . :)
ReplyDeleteYou did want feed back :) as I read your carb section and some of it is a bit wrong, eg the float bowl gasket was not square section it is round section but I see you fitted a round section anyway and the original O ring can be purchased rather than fit a too thick one as it can raise the float height if not done right, there are also various other areas that need attention on those carbs as they do tend to corrode and very soft metal but all can be sorted ok if you know what you are doing and also over tightening of certain areas can distort the parts and it can leak if not repaired or done properly, the top cap gasket should also be a thin paper gasket as its a measured distance and too thick a gasket will change the travel of the slide, there are various part changes for the carbs and some parts do fit but are not for some versions of Bing carbs for the Quicklys, also there are the changes of fuel mix ratios with modern oil and modern fuel that often need addressing as regards tuning of the carbs, as you may already know I fully restore the carbs for others, if you need help just ask , im on Facebook and in the NSU Quickly UK page where you can find me , Shane Woods . :)
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