This was supposed to be a response to the what carbs thread.

[BrianK]

But I guess I screwed it up and started a new thread...anyway...

I put 39mm Keihin flatslide FCRs on my 850, and I love them. I had put a pair on my Ducati 900SS and they positively transformed that bike, so I was predisposed to them. My 850 ran for about a minute with the Amals when I first got it, then wouldn't start again, so I don't have a great basis for comparison, but still I think the Keihins were a big step in the right direction based on what I hear about other alternatives.

Only downsides, beyond "non-stock" complaints, are cost - four figure$$ from CNW, perhaps a bit less from other sources, but I wanted to be able to call Matt Rambow if any problems (there weren't), and a HELL OF A TIGHT FIT. I didn't think they were gonna fit - no way. But I shoehorned them on. Have to hold left sidecover on with a cable tie (no room for dzus fastener anymore), and they do contact my right side petcock somewhat. Also, the air filter box, with attached ignition switch bracket has to go (substitute available from Norvil, as I understand it).

Now that I think of it, I've also had to rejigger my battery holddown arrangements, but I think that's because I put a huge electric-start-capable battery in there (which the bike sure doesn't need - this mod I regret and will probably reverse at some point) - not remembering which particular mod led to that issue. Readily resolvable, in any event (bungee cord!)

 

[Ron L]

I put 41mm flatslides on my 900SS SP and it transformed it. (Can you say second gear wheelies at will!). I have been intrigued by the 35mm CNW kit (or Sudco), but 39's!

Have you flowed the head? What cam are you using? I have thought of doing this on my 850 cafe bike ever since I saw them on Dreer's 880's.

The only other person I have spoken to who used this kit complained about difficulty dialing them in. Yours worked straight from the box?

 

[BrianK]

Apologies, I meant 35mm's! Got 'em from CNW.

Worked right out of the box. A bit difficult to put on, as I said, with "some DIS-assembly required," but they worked fine from the get-go.

My plugs read rich on past checks, but I just put on Dyna Coils which have really helped performance, and I have yet to check the plugs to see if the extra juice has taken care of the former richness issue. Those, by the way, are another great mod - at least, were for me. I had been backfiring madly, and occasionally shorting out and blowing the main fuse (I did other electrical cleanup as well, though, so the latter was not NECESSARILY related to the coils). Now she runs like a champ! (Knock on wood.)

No other engine mods, yet. Probably will have the heads breathed on at some point, but doesn't seem any imminent need for that.

- BrianK

 

[JimC]

I need new carbs on my 72 Combat. I've been trying to decide if the additional $700 for the Keihins over the Mikunis is worth it. Anyone have the experience of both?

 

[Ron L]

I need new carbs on my 72 Combat. I've been trying to decide if the additional $700 for the Keihins over the Mikunis is worth it. Anyone have the experience of both?

I have dual 34 Mikuni's on the cafe racer and have installled a couple of single 34 kits for friend's.

The dual 34's flow better and gave a definite seat-of-the-pants increase over the 32mm Mk1 concentrics. The single Mikuni kit gives good mileage and simpler tuning. My Mikuni's as well as my friend's have a tendency to have float sticking if they sit for very long. This results in them pi$$ing gas out the vent bowl until you rap the float bowl hard enough or failing that, pull the carbs and clean the bowl and floats. I do not have this problem with Keihin pumpers on the Duck.

I think the Keihin's would give maximum performance on a modified motor. The Mikuni's are a cost effective alternative. For a stock motor with minimal mods, I prefer sleeved concentrics over the single Mikuni option. YMMV

 

[JimC]

Thanks for the info, Ron. I'll probably go with the Mikuni single carb setup. Not the highest performer, but a lot less hassles.

I had a lot of dirty fuel issues when I first ran my Combat. I cleaned and cleaned and cleaned the tank, all to no avail. Still had enough dirt to foul the carbs (Amal). I installed a pair of Pingel inline filters. No more dirty fuel issues. Been running them for 8 years now. Found them at an Harley aftermarket shop. Used crimp-on ferrules to make a real neat looking job of it.

 

[BrianK]

Just ran across this: Brand new Keihin 35mm FCRs on fleabay, $875.

http://cgi.ebay.com/ebaymotors/NORTON-C ... enameZWDVW

 

[frankdamp]

I still don't understand the old motorcycle industry's predilection for multiple carbs. For donkey's years, larger American cars used two-choke or four-choke carbs, so there's only one float bowl and exterior linkage to mess with.

I've never considered a 4-cylinder classic Honda because I can't see messing about with four separate carbs, four throttle cables, four chokes, etc.

Moot point nowadays, I guess, since everything's gone to computer-managed fuel and ignition systems.

 

[BrianK]

Frank, I for one agree with you! Although, I must say I've been pleased with the FCRs, if I were on a stricter budget, I'd do a single Mikuni no if's and's or but's. Synching carbs is a fool's errand.

 

[billball]

I've never considered a 4-cylinder classic Honda because I can't see messing about with four separate carbs, four throttle cables, four chokes, etc.

Maybe my CBX's and early GoldWings aren't classic, but they only have 1 throttle cable despite 6 and 4 carbs per bike. Well, actually the GWs have two cables because the system is push/pull. And the chokes are all hard linked and never get touched once they leave the factory. The only time I ever mess with the carbs is if they get gummed up from sitting, and that's just a cleaning. Someday the o-rings will need replacement and the I may have to pull out the mercury stick and synchronize them. You're missing out on some nice bikes.

Bill in Alamo, CA
75 Commando
76 GL1000
79 CBX
82 CBX
91 600 F2

 

[bryan_woods]

I know this is probably sacrileges but has any one put a SS carb on a norton. Im really curious.

Regards Bryan