Throttle slide

Information relating to the Matchless G5 or AJS Model 8 350cc Lightweight
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Red Gauntlet
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Posts: 173
Joined: Wed Aug 19, 2020 11:22 am
Location: Dorset UK

Throttle slide

Post by Red Gauntlet »

Both my G5's have throttle slide 3 not 3&1/2 they run ok but why should someone replace the slides on both my engines with 3, I assume they should be 3&1/2 ?
Rangy65
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Joined: Tue May 07, 2013 11:35 pm
Location: LINCOLNSHIRE UK

Re: Throttle slide

Post by Rangy65 »

Hi Red check the parts book page 9 says part number 389-060 valve throttle - size 3-1/2. Carb should be 389 1-1/8 bore. My assumption is that someone may have had a performance issue and thought it was related to the throttle slides i.e mixture too weak. Larger the cutaway the weaker the mixture.
I fitted all four G5's that i have built over the years with the set up above without any issues. All were bog standard except for going up to 20T on the gear box output.
Cheers
Steve
Red Gauntlet
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Posts: 173
Joined: Wed Aug 19, 2020 11:22 am
Location: Dorset UK

Re: Throttle slide

Post by Red Gauntlet »

Yes it does say 3.5 for the slide but I was puzzled as to why both had a 3 in the carb, I also noted that there was another thread that said 3 not 3.5 I shall swap it over and see what happens. Performs ok with the 3 though.
vigo
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Posts: 114
Joined: Sat May 18, 2019 5:50 pm
Location: Cheshire UK

Re: Throttle slide

Post by vigo »

My G5, a non runner had a carb on it for a 500 machine. Returned to standard setup starting and running great but.......
I'm more I interested in Rangy65s comment on "20T on the gearbox output". This G5 seems to be under geared and anything more than about 42mph is painful.
Any tips?
Rangy65
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Posts: 434
Joined: Tue May 07, 2013 11:35 pm
Location: LINCOLNSHIRE UK

Re: Throttle slide

Post by Rangy65 »

Ok the easy way to alter the gearing is to change the rear sprocket as its a bolt on job like more modern machinery. The club spares scheme has just had some standard one's (55T) made up by a really well known sprocket manufacturer. So for the rear you need to go down on the number of teeth. I personally used B&C Express who are close to where i live in Lincs. Someone will probably know exactly how many teeth to drop down to but as a guess i would go to 52. The sprockets are made from Duraloy & hard anodised, not steel but they do wear well. You would need an old sprocket as a pattern. Villiers spares did have some different sizes as the same hubs were fitted to FB's.
Regards
Steve
Red Gauntlet
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Posts: 173
Joined: Wed Aug 19, 2020 11:22 am
Location: Dorset UK

Re: Throttle slide

Post by Red Gauntlet »

Looking at the 1957-1964 Matchless All Models Workshop Instruction Manual I find that the slide is listed as 3, last night I swapped it over to a 3&1/2 and looking at the cut away there is a small difference (1/32"), I will go for a run this evening and see if there is any discernible change in performance.
carb.JPG
I shall get a new rear sprocket for future use, I did not realise they were now available again.

From the parts list however it does state 3&1/2.
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Red Gauntlet
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Posts: 173
Joined: Wed Aug 19, 2020 11:22 am
Location: Dorset UK

Re: Throttle slide

Post by Red Gauntlet »

Road tested the bike last night 30 miles, indeed a good performance change, surprising really for such a small difference in the slide dimensions. so in conclusion 3&1/2 slide is the one to use.
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