Mixed set of carbs

[McTrucky]

Hi all,

Now started on the carbs on my 1976 rebuild.

The carbs appear in pretty good condition - they looked to have been partially drained before storage; so low tide marks on the floats and gunge in the bowls with cruddy looking jets etc. But I have seen much worse.

So I was getting round to ordering up some new rubber and noticed I have three carbs numbered 764A and one numbered 758A.

I think the 764A are 1977 and the 758A is 1976 model. The engine number is GL1E-2007625 and the chassis number also begins 2007 - I believe the bike is a 1976 model; but happy to be corrected.

My question is - will the same carb kits work across both carb types? Should I rummage through some spares I have with the bike and see if there is another 764A in there and make them all match?

Next question is.... based on the material I have read on here I think I should go with the Randakk's rebuild kit - is there anyone in Europe supplying these?

My reason of saying I want that kit is that I know I need the inlent manifold seals, and also the plemum seal which are included in that kit. The amount of silicon rubber everywhere tells me the last owner had fun trying to get everything sealed - the plenum are was covered in it. I also need the seal between the plenum and the airbox - this was just one big silicon gum fest, with no rubber seal at all. I see the airbox seal and also fuel/vacuum lines on ebay in the UK for not too much money - would you go with these, or seek Randakk supplied ones?

I am hoping to reuse the jets - BUT.... they are not branded, no K logo on them, and no size numbering. Likewise the floats appear aftermarket with no name on them. What do you think - reuse and hope for the best, buy a kit that comes with new brass and floats, or suck it up and buy Keihin/Honda ones....?

I am not keen on spending hundreds on this - but I would rather spend enough to get it right, than save a few quid and regret it every time I ride it. That said, I have Keyster jets in my Suzuki and am very happy, so would not worry about using them.

[gltriker]

Forum member, Old Fogey ( John Evans ) is your go-to man for Excellent advisements in Scotland and elsewhere
John Evans lives in Glascow, I believe.

https://www.wingovations.com/

Send him an email. There are several blue "email me " buttons on his Wingovations website.

just found this email address.

wingovations@googlemail.com

It may be the same connection that those blue button provide..

[Lucien Harpress]

I'll let the experts fill in the important info later, but here's what I gathered from my experiences with them-

--These are NOTORIOUSLY finnicky carbs, so eliminating as many problem areas as possible is always best.

-Mis-matched numbered carbs can probably be made to run decently, but if you can get a set matched to the proper year of the bike is best.

-If you're leaning Randakk, get the whole kit. It's not much more, and you know it'll be right.

-Never trust aftermarket jets, ESPECIALLY for these carbs. Again, they might be able to be made to work, but not as well as they should work. All factory jets are marked with a logo and number, even if it's small and faint.

Can't speak for importing things or parts aquisition, but you've come to the best place for info on these carbs. Best of luck!

[redglbx]

Personally, if done correctly these are easy carbs that will perform very well, I am not a fan of mix matching carbs, I just did a 76 bike (Ltd) that had 3 correct Ltd carbs and 1 78 that just happened to be a super lean California emmisions carb, it ran like shite to be polite ! So the 4th oe carb must’ve been damaged at some point. I ended up using another standard 76 carb & used the complete Randakks kit along with PJ’s Motirsports new jets (Honda).

The thing is that Randakks Kit is all made from Viton rubber that will resist the alcohol in today’s fuels, good stuff !

In my opinion if you cannot find a matching 4th carb then the set you have should work fine so long as all the jetting is the same among all 4, 76 & 77 are very closely related.

Silicone/rtv is an absolute terrible thing when exposed to fuels, it just dissolves and will not seal squat that way. They will work very well if you take your time and set them all the same and according to the Honda specs. Once done a really fine carb balance will be the icing on the cake. Cleanliness is also of utmost importance, no silicone/rtv used ! they simply cannot be clean enough.

On the jetting, if you have a good set of precision pin gages you can check & verify that they are the same size, but keep in mind that jetting is not only the hole diameter but also the length, most are sized by actual flow not just a hole size. So on jetting I prefer to use proper Honda spec jets, better quality on something that is critical for the proper operation of these carbs. Hope this helps

[robin1731]

While John at Wingovations is the closest to you, as Randakk approved rebuilders we are not supposed to sell rebuild kits. Only provide the rebuild service.

I never run aftermarket jets or float valve assemblies in GL carbs. Too many issues. You buy an aftermarket kit that has brass in it and it covers (usually) 1975-1979. There are too many jet and needle changes for that to work. You can try looking for good used original jets. Better than using aftermarket.

Also, try to get the correct carb for the one oddball that you have. Easier to do on this side of the pond I know but do what you can.

[ericheath]

If you haven’t gone here yet, please do, a wealth of information is here on a lot more than just carbs.

https://www.randakksblog.com/site-map/

Hope this takes you there. Two tech tips I have circled below. I believe but can say for sure your 758 carb body will work with 764A carbs as long as internals are changed. Only one jet- idle air jet- was different. See the posts on emulsion tubes as well.

0432B172-644D-4685-B0E8-CDDBFB3F323B.jpeg (183.64 KiB) Viewed 656 times

[McTrucky]

Thanks all. I have emailed John for his opinion and costs for parts.

I am minded to keep the mixed set of four carbs as thay are very similar, and if I am rebuilding them should be able to fit with the same jets sizes all round.

Will wait and see what John comes back with.

[robin1731]

Thanks all. I have emailed John for his opinion and costs for parts.

I am minded to keep the mixed set of four carbs as thay are very similar, and if I am rebuilding them should be able to fit with the same jets sizes all round.

Will wait and see what John comes back with.

Jet size may not be the only difference. Check that the jet needles are also the same.

[McTrucky]

Sorry for leaving this hanging.
I got John's input and kind of decided to attempt to get it back to original spec, which is the 758A models. I have one fitted to the bike (well, on the bench at the minute) and three in boxes, of unknown condition - but superficially don't look too bad.

But before buying all the new gaskets etc I am just going to see if I can get it running with what was fitted. Even if it is lumpy etc, at least it will prove if it will run. Be a shame to spend a load of money on refurbishing carbs for a bike that had, say, run its big ends.

The delay has been caused by me damaging the ligaments in my ankle, and am hobblling about on crutches. Hopefully not too serious, and I can start putting weight on it in the next couple of days and be back to the shed next week.

[pidjones]

Hope you heal quick. Lots of good info here on carbs, BUT - have you changed the belts? Do so BEFORE attempting to start. The RTV is evidence of not the best care, and this is an interference engine. Hopefully no RTV is in other parts of the engine. A small bit that I failed to find had been left in one of mine. Found its way to the oil restrictor for the right head. Totally stopped oil flow, binding and snapping the cam in the middle.

[McTrucky]

Hope you heal quick. Lots of good info here on carbs, BUT - have you changed the belts? Do so BEFORE attempting to start. The RTV is evidence of not the best care, and this is an interference engine. Hopefully no RTV is in other parts of the engine. A small bit that I failed to find had been left in one of mine. Found its way to the oil restrictor for the right head. Totally stopped oil flow, binding and snapping the cam in the middle.

Thanks, appreciate that.

Yes belts done. The ones that came off looked like new though, which slightly worries me that the thing broke down, belts were changed, it didn’t start and was parked up.

Hence why I hope to get the engine running before spending a lot of extra money making it how it should be.

[Sidecar Bob]

There's nothing wrong with using silicone sealant on engine gaskets if done properly. Anyone who knows what they are doing would apply the silicone (either a small bead or a film so thin you can only tell it is there by the sheen) ahead of time and allow it to fully cure (at least overnight) before assembly. The problem comes from people who don't know what they are doing and put things together while the sealant is still wet so that it can squeeze out from between the mating surfaces.
Not to mention using it on carbs where the gasoline can attack it (note that I have been known to apply a small amount of silicone sealant around the outside edge of the float bowl gaskets on carbs for my winter machine, assemble with it wet and smooth the squeeze out over the line where the bowls meet the bodies to prevent salty water from causing corrosion but I don't do that on the summer bike).
Is silicone sealant on gaskets a good idea? I've seen both Honda and Harley gaskets that came from the factory with cured beads of silicone on them.

BTW: "Room Temperature Vulcanizing" refers to any rubberlike compound that cures without heat. This can be silicone sealant but it could also be any number of other materials that don't need heat to cure.
Calling silicone sealant as "RTV" is lazy and imprecise and we should stop doing it. It is like saying that you put "liquid" in the crankcase when you mean "oil".

[McTrucky]

It starts!

Very lumpy at first, clouds of blue smoke, but big step forward.

I couldn't let it run for more than a few seconds as there is no water in it. But the light at the end of the tunnel is there. I'll create a new post wrt the water.