Carb Slide Wear

[Worty]

Why is it that the slides get scratched up like that?   My Amal was brand new 10 years ago and covered 10k miles, but I still have scratches on the slide (not really bad though).  Always run with an air filter - the only thing I can think of is RM applied some broken glass thinking that may improve its performance??

[muskrat]

G'day Fellas.
I have a foot in both camps  No not like that
The two 30mm Keihin PWK's (same as the JRC) on the Cafe are great. 1st or 2nd kick starter, first time ever it idles (once warm). They were a PITA to get tuned right but not as bad as a Mikuni. Might be OK on a standard machine. The slides are chromed but still wear (no air filters).
The new Premier Amal 932 on the A7 plunger (again not standard) is a "god send". I did have to change the pilot jet but that is easy from the outside now and the main jet. Starts 1st or 2nd kick, idles and revs out clean.
Cheers

[Colsbeeza]

I had my Monobloc slide resleeved last month with a stainless steel sleeve and the body distortion sorted, at very reasonable cost. I did this because I had already fitted all new jets, float needle, float bowl cover etc. it has performed perfectly until I overtightened the bolts . It is now like new. A new monobloc will see your pocket emptied by about A$600.
Before going for a new carb, I recommend you  consider getting your old carb checked overall for condition and repaired if feasible. There seem to be many firms offering this service.
Col

[Magista]

For $137.26 USD to my door...I'm going with the new JRC rather than a new Amal or resleeving the old one. It makes sense from a price point, quality, and performance standpoint. If I was worried about originality, I would go Amal.

Note: The Mikunis on my CL350 were not difficult to tune. As far as the casting of Mikuni vs JRC...I'm looking at both right now, they are the same. There are Chinese copies with not so great casting so that could be what some have seen. I'm seeing a good quality product.

[RDfella]

Have to say one would be hard pressed to find a better made product than the Mikuni - die cast body, chrome-plated brass slide ...
Just two issues - to get the float out requires pushing out its retaining shaft, which is a press fit in two spindly pillars (break either of those and you need a new carb body) and the tuning ...... The needles are not a taper but a succession of ten differing steps and with several dozen needles to choose from (the needle could be rich at bottom, lean 1/3 way up, rich again then lean at the top - or humpteen variations on the theme). That and the twenty or more different needle jets, it is no wonder so many despair of setting these carbs up. And to crown it all changing one jet affects all the others. Basically one can set them up to start easily or run well - but never both. To get one set up correctly would require a full box of jets and unlimited time on an engine brake checking mixture at 1/10th throttle openings. Few if any of us have the time, money or equipment to do that. I certainly don't, which is why I binned two new Mikunis and fitted Amals.

[Worty]

Have to say one would be hard pressed to find a better made product than the Mikuni - die cast body, chrome-plated brass slide ...
Just two issues - to get the float out requires pushing out its retaining shaft, which is a press fit in two spindly pillars (break either of those and you need a new carb body) and the tuning ...... The needles are not a taper but a succession of ten differing steps and with several dozen needles to choose from (the needle could be rich at bottom, lean 1/3 way up, rich again then lean at the top - or humpteen variations on the theme). That and the twenty or more different needle jets, it is no wonder so many despair of setting these carbs up. And to crown it all changing one jet affects all the others. Basically one can set them up to start easily or run well - but never both. To get one set up correctly would require a full box of jets and unlimited time on an engine brake checking mixture at 1/10th throttle openings. Few if any of us have the time, money or equipment to do that. I certainly don't, which is why I binned two new Mikunis and fitted Amals.

I love riding bikes, I like fixing them, but I don't have the time, inclination, expertise or equipment to do stuff like this.  Even with the Kwaka, if it needed valve shim adjustment, I'd have to get to a bike shop that exchanged shims, then go back and do the work.  Makes me wonder if just getting the bike serviced (valves and carb balance) occasionally may be a better option for it??  Everything else is fine, plugs, oil changes, brakes, etc, etc, but I don't want these things to keep me off the road.

Suppose I'm a bit in the middle - can't rebuild the motor like Bergs, but can do most other things to a point.

[Rex]

Have to say one would be hard pressed to find a better made product than the Mikuni - die ca

Never bought an after-market Mikuni but many say how good they can be. OK if you have endless access to a rolling road and a lot of time, but as I don't have either I'll stick to the Amal compromise.

These many and  various needles that are available; does the carb need setting up for the individual bike (assuming it's standard of course) or just the generic model? If it's the latter don't the Mik owners like to share their experiences or would they rather keep schtum over what they've discovered?

[Magista]

Tuning Mikunis is not as hard as ya'll are making it out to be. I've installed and tuned a pair on my CL350. Runs strong and pulls hard throughout the entire range.

Anyway...back to the Keihin/JRCs.

I need carb mounting studs. My bike is a '58 A7 and has mounting bolts. This means I need studs with the same threads on each end. I've found them with 26 and 22 TPI but not the same. Can anyone point me in the right direction? I'm in the US and have checked Steadfast and Classic British Spares already.

Thanks!

[Slymo]

The body isn't always worn. I put a new hard anodized slide in my original 376 on my A10 and its well within tolerance. I always think its a shame to stick new equipment on a classic machine. Those witness marks don't necessarily mean that much either. Take the carb off and put a finger down each side of the throat and see how much the slide moves back and forth. Even if the body and the slide have both worn the same amount a new slide will logically reduce the wear factor by 50%. I my case the slide had worn considerably more than the body so all was good. Finally it is quite possible to either bore and sleeve the body or to bore the body and sleeve the slide. I have done both with complete success. I have a brass sleeved 389 on one bike and the aforementioned 376 on the BSA both work perfectly.

[Magista]

Got around to installing the PWK/JRC. Had to order a few nuts and a pair of studs to mount it to the manifold (thank you Steadfast Cycles).

After a few kicks she fired right up. Once warm and a little idle adjustment, she settled into a nice tickover. I'm waiting on my pancake filter then she'll be pretty much ready for a test ride. We'll see how it does throughout the range.

So far I'm pleased with the quality, simplicity, and cost of the carb.

[Magista]

I just returned from taking the bike out for a spin. Here's my carb report.

Throttle response is very good and smooth. Better than the Amal and better than my Mikunis (I may even replace the Mikunis on my CL350 with a pair of PWKs). It pulls well through out the range. The bike feels very good. Absolutely zero complaints.

For my application, '58 500 twin single carb, it was the right choice. The jetting was spot on out of the box. From cost, to ease of install, to functionality it really can't be beat.

[muskrat]

G'day Magista.
Great to hear.
A lot easier when the bike is close to standard. I'd hate to start from scratch with my carbs/motor.
Cheers

[Colsbeeza]

Hi Magista, It seems to be very good value for money. A great option if originality isn't your priority.
Col