Keihin FCRs/Mikuni HSR42s vs. PHM40s - Dyno Comparisons?

[Kristian]

Hello,

New poster; nice forum! I'm pondering buying my second carb Sport--first one was in late 1994, sold 1997. It's one of two or three bikes of 13 owned that really stuck with me. To go with the full Staintune system, Raceco's Manfred recommended Mikuni HSR42s, which had just become available. It took a lot of faffing to install, but, they worked well, though I never did dyno comparisons. Has anyone ever done a dyno comparison between these carbs? If there aren't enough of a gain, my older, more objective self can't see spending $$ on Keihins or HSRs. I might expect more area under the curves--but how much more?

Thanks-

Kristian

[Rough Edge racing]

Hello,

New poster; nice forum! I'm pondering buying my second carb Sport--first one was in late 1994, sold 1997. It's one of two or three bikes of 13 owned that really stuck with me. To go with the full Staintune system, Raceco's Manfred recommended Mikuni HSR42s, which had just become available. It took a lot of faffing to install, but, they worked well, though I never did dyno comparisons. Has anyone ever done a dyno comparison between these carbs? If there aren't enough of a gain, my older, more objective self can't see spending $$ on Keihins or HSRs. I might expect more area under the curves--but how much more?

Thanks-

Kristian

 One Mikuni HSR 42 is normally used on a 1200-1400 cc Harley and I believe it can support  90 HP.... How much power increase you get always depends on engine tune with the intake, cam and exhaust all working as one...
 When you did the swap years ago was it worth the effort on a street bike?

[rocker59]

I'm running Keihin FCR41s with a K&N filter in the stock airbox, and full Staintune.

Dyno is in the low 80s with a much smoother curve than it had with the Dellortos and Marsee crossover.

Nice improvement in power, but more noticeably the driveability improved, the fuel economy improved, and the effort required to twist the throttle was greatly reduced.

Full Staintunes are not currently available new, so they might be hard to find.  $2450 when last offered.  The Keihin FCR41 kit will be $1000 +/-.  I got mine from SUDCO.

[Kristian]

I'm running Keihin FCR41s with a K&N filter in the stock airbox, and full Staintune.

Dyno is in the low 80s with a much smoother curve than it had with the Dellortos and Marsee crossover.

Nice improvement in power, but more noticeably the driveability improved, the fuel economy improved, and the effort required to twist the throttle was greatly reduced.

Good stuff, thanks. That sounds very worth while; the bike I'm thinking of has a full Termi system. I do recall the HSRs had much lighter pull, and seemed smoother.

Best,

Kristian

[ed@guzzipower.com]

Unless you are  building for top end power and blowing thousands of dollars on cam, carbs, exhaust, heads, etc- , you don't need $1000 carbs. Spend $60 and jet the stock dellortos correctly and enjoy the bike.

ed

[Arizona Wayne]

For a lighter throttle a $11 Throttle Rocker works.     Or maybe the `97 on up Sporti (efi) have a lighter throttle and w/fuel injection instead of carbs you're good to go. 

[rocker59]

Unless you are  building for top end power and blowing thousands of dollars on cam, carbs, exhaust, heads, etc- , you don't need $1000 carbs. Spend $60 and jet the stock dellortos correctly and enjoy the bike.

ed

Ed,

As I'm sure you know, the Dellortos on the Sport 1100 have a VERY heavy pull, and nearly 1/2 turn from closed to full.  For me, that made the riding experience less than lovely.  Even after changing the springs, I didn't like the big Dellortos.

Personal preference, but the improvement in riding enjoyment with the FCR41s was worth the price.  The performance improvement was icing on the cake.

[guzzisteve]

There is also a smaller(larger?) diameter throttle for better action to WFO, otherwise you need 2 hand fulls.

[rocker59]

There is also a smaller(larger?) diameter throttle for better action to WFO, otherwise you need 2 hand fulls.

Yeah.  First thing I tried was a larger diameter throttle.  1/4 turn was nice, but at the expense of even more effort.  Never tried a smaller throttle because I didn't want a longer turn.

The stock throttle couldn't be taken from the idle stop to WFO in one motion.  It required a second take.  Doing that got tiring at the track, or on a curvy piece of 2-lane blacktop.

[Kristian]

Unless you are  building for top end power and blowing thousands of dollars on cam, carbs, exhaust, heads, etc- , you don't need $1000 carbs.

ed

This is probably true for WFO track conditions, where response throughout the powercurve isn't as quite as important as on the street--and there, by all accounts, FCRs fuel significantly better. I've seen the response of FCRs on a stock 1100; it is way more responsive right off idle, like a different bike. Same with the HSR42s I had once.

[ed@guzzipower.com]

The Keihins work well- they're a more modern design than the PHF's. Roller bearings on the slides, cammed slide action etc. But with  a handful of jets, adjustment of slide springs and the right throttle cam, you can make the PHF's work well.

[Kristian]

The Keihins work well- they're a more modern design than the PHF's. Roller bearings on the slides, cammed slide action etc. But with  a handful of jets, adjustment of slide springs and the right throttle cam, you can make the PHF's work well.

You are right, I did get them to work well, after quite a bit of faffing about and an afternoon of dyno time!

And--there's still something about big Dell'Ortos; they're legendary, having been the go-to for fast bikes since forever. Even BMW used them to turn the /6 into the R90S. And they work quite well; hence my hesitation...

[pressureangle]

errrr...carb threads lol.

A rule of thumb is, if the motor can pull the main jet at WOT, it's not too big. Bigger hole makes more power, almost always.

The hard part is what happens below that. Throttle sensitivity goes up exponentially with bore size. Big carbs are trickier to jet and harder to drive.

But to the specific question, I had a big-inch high-power Harley back in the '90's, and had carbs donated by everyone, I mean everyone, to be the carb on it that made the most power. I had Lectron, Mikuni, Keihin, everything out there except Weber. At the end of the day, the 41.5mm Lectron, 44mm taper-bored Mikuni, Keihin FCR40 all made 105 rwhp. The S&S Super G with custom manifolding made 106 rwhp, and the S&S Super D made 113. This was a stock HD cases and HD cylinder heads 96" Shovelhead, to boot.

Drivability was best by far with the Keihin, though the thing was a straight beast with the Super D and that's what I drove it with. Given my '85 LM1000 with 11:1 compression, RHC ported heads, Web 86b cam and BUB exhaust making 68 rwhp with a lot of room for improvement and your engine being bigger, taking into account the throttle response and sensitivity I'd think you'd do well to stay with 40's. Just my $.02.

[salsaman1964]

I've fitted a set of Keihin FCR 37's to my Lemans 3 and a set of Mikuni HSR42's to my V1100 sport engine lemans 4. Jetting was done following advice from the V11 lemans forum for the Mikunis and the Ducati forum for the Keihins. Once you have a base setting to start from its a matter of trail and error to get it running right throughout the rev range.
The biggest improvement in both cases is the lightness and easy pull of the throttle. Tickover is perfect once warmed up and the smoothness of the throttle response is fantastic.
Obviously being a tight fisted Yorkshireman I didn't buy new. Its just a question of being patient and buying individual carbs on ebay when they come up. All the jets and needles are readily available.
I would say that if you are thinking of trying this conversion then give it a go. A smooth running tonti framed Guzzi with a light throttle and carbs is hard to beat.

[Turin]

You can go the quick route. Cheaper than Sudco -  http://www.power-barn.com/moto-guzzi-1100-keihin-fcr41-carburetor-kit/

They will set them up for you ( altitude, exhaust, engine mods etc. ) Save you the cost of some dyno time.

[Kristian]

Snip
They will set them up for you ( altitude, exhaust, engine mods etc. ) Save you the cost of some dyno time.

Yep, but, if I do it, I want to see what the actual gains are. If any. $1550 for FCRs now. Call it two grand with install and dyno time. Ouch.

Best,

Kristian

[Kristian]

I've fitted a set of Mikuni HSR42's to my V1100 sport engine lemans 4. Jetting was done following advice from the V11 lemans forum for the Mikunis snip

Salsa, I installed a set of HSRs on a Sport 21 years ago, bought from Raceco, but, never faffed with the jetting. Do you mind divulging what your HSR jetting specs ended up being, and which throttle/cable components you ended up getting from Venhill? I recall doing that myself way back when, but, have no recollection of how long the cables were. I'm fixin' to buy another carb Sport.

Thanks,

Kristian

[salsaman1964]

Hi Kristian
I bought a make your own cable kit from venhill and a 2 into one cable splitter. The HSR's are set up for a pull push throttle but I only bothered with the pull and haven't experienced any adverse effects shutting the throttle off. 
I cant remember the settings off the top of my head but I have them written down somewhere over at my garage. I'm going over at the weekend so I'll try and find them. I'll also measure the cables
The HSR's actually worked ok out of the box once the accelerator pumps were disconnected which is easy to do by removing the plunger rod. You also need to block the vacuum vent at the top of the carb. I just ran a tube from one to the other carb.
The HSR's are a far cheaper than the FCR's and in my opinion work really well.
I'd also recommend trying a Frando hydraulic clutch slave cylinder with a 17mm master cylinder. It make the clutch lever very light.
Venhill do them but you can buy them cheaper on the net. The V1100 sport is a cracking bike but the original clutch and throttle are far too heavy.
Regards Tony.

[Kristian]

Snip
Given my '85 LM1000 with 11:1 compression, RHC ported heads, Web 86b cam and BUB exhaust making 68 rwhp with a lot of room for improvement and your engine being bigger, taking into account the throttle response and sensitivity I'd think you'd do well to stay with 40's. Just my $.02.

If a true 11:1, have you considered knocking that back to 10:1? There are good reports--from Germany's Dynotec, one of the world's best Guzzi tuning shops--that 10:1 is a real limit on these 2V Guzzis. High piston crowns + poor gas apparently cause all sorts of complicated problems...

Best,

Kristian

[Murray]

The Keihins work well- they're a more modern design than the PHF's. Roller bearings on the slides, cammed slide action etc. But with  a handful of jets, adjustment of slide springs and the right throttle cam, you can make the PHF's work well.

Less crap, the difference is night and day not in ultimate dyno numbers but in every single part of the rev range, engine response, been able to finely modulate the throttle, their tune doesn't go walkies every 5000kms and its as good as excuse as any to get rid of the convoluted throttle cable setup the sports were saddled with.

[salsaman1964]

FAO Kristian
This is the set up recommended to me by a Carb guru John in California for the HSR's
Needle J8-8DDY1-98 4th clip from top - washer underneath(stock)
Pilot Jet VM28/486 30
Air Screw 1 3/4 turns out
Main Jet 150
Accelerator pumps set to 0
Main Air Jet REMOVED
I followed his recommendations and but used some velocity stacks and foam air socks. the Air box was removed.
I also used a set of the plastic air intake manifolds from Stein Dinse.
Regards Tony

[pressureangle]

If a true 11:1, have you considered knocking that back to 10:1? There are good reports--from Germany's Dynotec, one of the world's best Guzzi tuning shops--that 10:1 is a real limit on these 2V Guzzis. High piston crowns + poor gas apparently cause all sorts of complicated problems...

Best,

Kristian

No apparent issues. No pinging, knocking, or signs of detonation. I have a lot more tuning to do before I get that complicated. And even if the top end may benefit by lower compression, I like the midrange improvement if it doesn't come with tiny hammers in the engine.

[Dukedesmo]

Quote from: salsaman1964 on January 22, 2017, 08:28:39 PM

I followed his recommendations and but used some velocity stacks and foam air socks. the Air box was removed.
I also used a set of the plastic air intake manifolds from Stein Dinse.

Totally different setup I know but I have Keihin FCR41s on my Ducati 900 Monster with no airbox.

When I set them up at the dyno, sock filters over the (stock) stacks cost me 5hp at the top end but no real change in midrange - the K&N stacks with filter fitting provision (and K&N filter) work much better for me.   

[ZepGori]

https://m.facebook.com/groups/1381982031882185/permalink/4609777085769314/

Hi all
Following this old topic, I share some tests done last months with friend of mine: Roberto Betti, Italian tuner and winner in Vintage Italian Championship.
After some experiences on track and overall on road, on different Guzzis (from stock 850 LM3 to overbored 92x78, 94x78 and 95x80mm) definitely these cheap Chinese FCR and HSR work very well.
Top results with HSR 45mm and long stacks.

https://m.facebook.com/groups/1381982031882185/permalink/4609777085769314/