Mikuni RS question this time
- Thread starter Spondonrider
- Start date
Cosi
Hero member
- Location
- Kingscliff
Vince, The Rooters got one for sale if your interested in fixing your mid life crisis 
Dellortoman
Hero member
- Location
- Tasmania, Australia
Thanks for the offer of a choke cable setup Red. Email sent.
PS: Message to the pedants of the world ...
Yes, I know it isn't really a choke, but we seem to be lacking a word in the english language to describe a mixture enriching jet for cold starting. Maybe Henry could invent one.
Cam
PS: Message to the pedants of the world ...
Yes, I know it isn't really a choke, but we seem to be lacking a word in the english language to describe a mixture enriching jet for cold starting. Maybe Henry could invent one.
Cam
laverdakeith
Hero member
You could just call it the cold start circuit because that is what it is, sadly not a very exotic name but fathomable by pedants and speakers of regular English the world over. Even henry. 
Keith
Keith
Dellortoman
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- Location
- Tasmania, Australia
Finally got around to installing the cable operated choke conversion in the Mikunis (thanks Red). It works a treat, and with the choke knob removed off the left side it doesn't foul the fuel tap. I took the bike for its first run with the Mikunis today.
First thing I noticed was the much lighter throttle, which creates an illusion of better throttle response until you get used to the feel of it. The bike is noisier due to the increased induction noise of the pod filters, over the standard air box, but I don't mind that. I quite like being able to hear the engine gulping air. I couldn't say whether the engine is running better than with the Dellortos, but it feels at least as good.
Initial jetting recommended by Red is pretty close to right. Engine runs nicely at all throttle openings. I don't reckon I'd get it any better by the seat of the pants tuning, so might book it on the dyno just to see if it needs any fine tuning. I dunno whether the bike is making any more power, but I think it has a smoother transition when opening it up from a trailing throttle. I suspect it's running a little leaner than the Dellortos at small throttle openings because it coughs and splutters until warmed up, but smooths out if I pull the choke on a bit. Once it's warmed up it's fine. Definitely needs the choke for starting.
I'm not sure whether the accelerator pump is operating properly. The engine bogs if the throttle is whacked wide open at low revs (below 4000rpm) but at higher revs it's OK. Not really a problem though. It's not as if I'm in the habit of giving it full throttle at 3000rpm. It picks up smoothly if the throttle is rolled on a little more slowly.
Overall impression of the Mikunis so far - not bad. I'm not as enthusiastic as Bevelman (what have you done with your Laverda thread), so I wouldn't say it's made a huge difference. Maybe my Dellortos were doing a pretty good job beforehand. I had them tuned as good as I could get them. Anyway, we'll see what the dyno says. But that'll have to wait until my dyno man gets back from his holidays - bloody indolent layabout.
Cheers,
Cam
First thing I noticed was the much lighter throttle, which creates an illusion of better throttle response until you get used to the feel of it. The bike is noisier due to the increased induction noise of the pod filters, over the standard air box, but I don't mind that. I quite like being able to hear the engine gulping air. I couldn't say whether the engine is running better than with the Dellortos, but it feels at least as good.
Initial jetting recommended by Red is pretty close to right. Engine runs nicely at all throttle openings. I don't reckon I'd get it any better by the seat of the pants tuning, so might book it on the dyno just to see if it needs any fine tuning. I dunno whether the bike is making any more power, but I think it has a smoother transition when opening it up from a trailing throttle. I suspect it's running a little leaner than the Dellortos at small throttle openings because it coughs and splutters until warmed up, but smooths out if I pull the choke on a bit. Once it's warmed up it's fine. Definitely needs the choke for starting.
I'm not sure whether the accelerator pump is operating properly. The engine bogs if the throttle is whacked wide open at low revs (below 4000rpm) but at higher revs it's OK. Not really a problem though. It's not as if I'm in the habit of giving it full throttle at 3000rpm. It picks up smoothly if the throttle is rolled on a little more slowly.
Overall impression of the Mikunis so far - not bad. I'm not as enthusiastic as Bevelman (what have you done with your Laverda thread), so I wouldn't say it's made a huge difference. Maybe my Dellortos were doing a pretty good job beforehand. I had them tuned as good as I could get them. Anyway, we'll see what the dyno says. But that'll have to wait until my dyno man gets back from his holidays - bloody indolent layabout.
Cheers,
Cam
Laverdalothar
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- Location
- Germany
Hi Cam,
the saying goes that "to make use of the lat slides you first have to learn how to use them", which means: Due to the bigger inlet, on a relatively standard engine it can make the bike even to stall if you open the throttle f.e. in idle to full open at once. Flat sliders need a bit more sensible hand. That is also due to the fact that they fully open with - say - 1/2 turn of the throttle while the Dell'Ortos need at least one full turn. Each degree you turn the throttle, the slider moves twice as fast as on the Dell'Ortos. So - a bit more careful use of that device is recommended...
The real big difference comes into play once the bike is tuned and has bigger pistons or longer valve durations or a gas-change supporting exhaust system (e.g.: breathes better). THEN really the larger carb and all the fanciness comes into play.
You can make a difference on your current setup by installing power-blades into the bellmouthes or into the manifolds (I prefer the ones in the bellmouthes, but you could even try both). These blades do separate the stream of air going into the carb by basically splitting the bellmouthes inlet channel horizontally in two sections, low to half and half to full. Widely used on KTM's f.e. in Keihin carbs, I could imagine they do their job on Mikunis, too.
I have both the 1000 SFC and the Jota equipped with these blades (hand-made out of stainless steel) and my gut feeling says they do work well. Nothing you can measure on a normal acceleration dyno though, as once you start producing power on these, you are already above half opening. A water braked dyno would maybe show the difference...?!? Not sure...
All the best
Lothar
the saying goes that "to make use of the lat slides you first have to learn how to use them", which means: Due to the bigger inlet, on a relatively standard engine it can make the bike even to stall if you open the throttle f.e. in idle to full open at once. Flat sliders need a bit more sensible hand. That is also due to the fact that they fully open with - say - 1/2 turn of the throttle while the Dell'Ortos need at least one full turn. Each degree you turn the throttle, the slider moves twice as fast as on the Dell'Ortos. So - a bit more careful use of that device is recommended...
The real big difference comes into play once the bike is tuned and has bigger pistons or longer valve durations or a gas-change supporting exhaust system (e.g.: breathes better). THEN really the larger carb and all the fanciness comes into play.
You can make a difference on your current setup by installing power-blades into the bellmouthes or into the manifolds (I prefer the ones in the bellmouthes, but you could even try both). These blades do separate the stream of air going into the carb by basically splitting the bellmouthes inlet channel horizontally in two sections, low to half and half to full. Widely used on KTM's f.e. in Keihin carbs, I could imagine they do their job on Mikunis, too.
I have both the 1000 SFC and the Jota equipped with these blades (hand-made out of stainless steel) and my gut feeling says they do work well. Nothing you can measure on a normal acceleration dyno though, as once you start producing power on these, you are already above half opening. A water braked dyno would maybe show the difference...?!? Not sure...
All the best
Lothar
Dellortoman
Hero member
- Location
- Tasmania, Australia
Mikunis seem to have improved the fuel efficiency of my Jota. With the Dellortos, I was getting just over 200km out of a tank before going onto reserve. Just got back from a ride with the Mikunis, and the trip meter is 249km since I filled up, and it's not yet on reserve.
When I first got the bike, I couldn't make 150km before hitting reserve. Dialling the cams got it to 200km, now the Mikunis have stretched it to 250 (or more? - dunno yet). I like these 50km improvements in range. Now seriously tempted to do the TPS thing to see if I can get another 50km
Cheers,
Cam
When I first got the bike, I couldn't make 150km before hitting reserve. Dialling the cams got it to 200km, now the Mikunis have stretched it to 250 (or more? - dunno yet). I like these 50km improvements in range. Now seriously tempted to do the TPS thing to see if I can get another 50km
Cheers,
Cam
mcnicol
Hero member
- Location
- Safety Harbor, Florida, USA
Cam, George Dickel (ask Red) seems to have exacerbated my ethanol-stimulated lucidity (at the expense of comprehensibility), and I have a response for you. But I am more then a little well-lubricated so I apologise in advance for inherent deficiencies or deficient incoherencies, I just can't see blind people wearing glasses any more...
My Mikuni RS carburetors (that's a really hard word to type when you're this drunk) have given me a 42% increase in fuel economy over my well-set-up-but-over-30-year-old -Dellortos. I was getting about 130-135 miles before I went to reserve from my "Jota", but that was all I ever got from my '73 3c when the Dellortos were brand new. 150-65 miles for my "Jota".
Now to be fair, I installed the Mikuni RS36s at the same time as a Redax/Sachse ignition, so fuel mileage figures looking at the Dell'Orto/Mikuni swap/upgrade may be a bit subjective.
Bloody hell I'm drunk.
But even making allowances for my socially-selected-ethanol-"enhanced"-condition", Miikuni RS36s's are da bomb diggity for Laverda triples, 180 (perfection mechanically incarnate) or 120 (yeah, OK), but really only perfect when used with Redax/Sachse ignitions. There are other post-modern (or even remotely-modern alternatives), check the archives, and find a local guy with a minimum of 2 connected synaptic neurons, like Wolfgang or Andy, or Piet or Keith or Red or Scott. Your local guys used to exist once, at least try to find them, give them a chance.
Still drunk, but getting more philosophical, OK for a Monday night (whatever that signifies).
Ken
My Mikuni RS carburetors (that's a really hard word to type when you're this drunk) have given me a 42% increase in fuel economy over my well-set-up-but-over-30-year-old -Dellortos. I was getting about 130-135 miles before I went to reserve from my "Jota", but that was all I ever got from my '73 3c when the Dellortos were brand new. 150-65 miles for my "Jota".
Now to be fair, I installed the Mikuni RS36s at the same time as a Redax/Sachse ignition, so fuel mileage figures looking at the Dell'Orto/Mikuni swap/upgrade may be a bit subjective.
Bloody hell I'm drunk.
But even making allowances for my socially-selected-ethanol-"enhanced"-condition", Miikuni RS36s's are da bomb diggity for Laverda triples, 180 (perfection mechanically incarnate) or 120 (yeah, OK), but really only perfect when used with Redax/Sachse ignitions. There are other post-modern (or even remotely-modern alternatives), check the archives, and find a local guy with a minimum of 2 connected synaptic neurons, like Wolfgang or Andy, or Piet or Keith or Red or Scott. Your local guys used to exist once, at least try to find them, give them a chance.
Still drunk, but getting more philosophical, OK for a Monday night (whatever that signifies).
Ken
im hitting reserve about 200 odd kays(fairly hard riding)-used to be about 160 ish
love the way you can hit the tit cold and she just sits there idling-my mates gpz900
would pull away at 160 plus-had a roll on the other day and i pulled away strongly(new clutch as well)
he gave up at 220
love the way you can hit the tit cold and she just sits there idling-my mates gpz900
would pull away at 160 plus-had a roll on the other day and i pulled away strongly(new clutch as well)
he gave up at 220
Dellortoman
Hero member
- Location
- Tasmania, Australia
I spent a couple of hours messing about on the Dyno to see what the carbies were doing.
Started off with 122.5 mains, middle notch on the needle (forget the needle /jet specs) and 18mm float height. First run showed that ot was too rich in the middle and too lean at WOT.
After a bit of fiddling and about 8 or 9 runs on the dyno we finished up dropping the float heights by 2mm (to 20), dropping the needles to the top notch and opening up the mains to 130.
It's still a wee bit rich in the middle but not too bad. WOT is pretty much spot on, although it varies a bit as the revs change - probably as the pipe goes in and out of resonance. The bike seems to be running OK although it still pops and cackles a bit on closed throttle (more than it did on the Dells). There doesn't seem to be enough adjustment in the mixture screws so I may need to increase the idle jets.
Was it worth swapping the Dellortos for Mikunis?
Well, there's bugger-all improvent in performance or rideability. The bike is making exactly the same peak power at the rear wheel as it was with the Dells - 76.2 RWHP. I guess that means about 85 HP at the crank.
Improvements are a slight increase in mid-range grunt and an improvement is fuel consumption. Throttle action is also lighter.
What has got worse is the idle, and transition from idle to first crack of the throttle is a bit fluffy. I might be able to sort it with a bit more fiddling and/or new idle jets. The Mikunis are also a lot noisier than the Dells, but I've gone from the original air box to pod filters, so the intake noise is less muffled.
Was it worth the cost and stuffing about - probably not, but it was an interesting learning experience. Maybe the Mikunis will pay for themselves out of the savings in fuel costs, if I live long enough!
BTW, checked ignition timing too by tweaking it up and down and looking at power output, but the 29 deg advance I had turned out to be optimal, so it ended up not changing.
Cheers,
Cam
Started off with 122.5 mains, middle notch on the needle (forget the needle /jet specs) and 18mm float height. First run showed that ot was too rich in the middle and too lean at WOT.
After a bit of fiddling and about 8 or 9 runs on the dyno we finished up dropping the float heights by 2mm (to 20), dropping the needles to the top notch and opening up the mains to 130.
It's still a wee bit rich in the middle but not too bad. WOT is pretty much spot on, although it varies a bit as the revs change - probably as the pipe goes in and out of resonance. The bike seems to be running OK although it still pops and cackles a bit on closed throttle (more than it did on the Dells). There doesn't seem to be enough adjustment in the mixture screws so I may need to increase the idle jets.
Was it worth swapping the Dellortos for Mikunis?
Well, there's bugger-all improvent in performance or rideability. The bike is making exactly the same peak power at the rear wheel as it was with the Dells - 76.2 RWHP. I guess that means about 85 HP at the crank.
Improvements are a slight increase in mid-range grunt and an improvement is fuel consumption. Throttle action is also lighter.
What has got worse is the idle, and transition from idle to first crack of the throttle is a bit fluffy. I might be able to sort it with a bit more fiddling and/or new idle jets. The Mikunis are also a lot noisier than the Dells, but I've gone from the original air box to pod filters, so the intake noise is less muffled.
Was it worth the cost and stuffing about - probably not, but it was an interesting learning experience. Maybe the Mikunis will pay for themselves out of the savings in fuel costs, if I live long enough!
BTW, checked ignition timing too by tweaking it up and down and looking at power output, but the 29 deg advance I had turned out to be optimal, so it ended up not changing.
Cheers,
Cam
G
Grant
Guest
Cam, Red has a Mikuni setting spreadsheet. Send him your settings or add the data yourself. I saw it once but don't know where it is these days.
markQLD
Hero member
- Location
- QLD Australia
good work grasshopper,, please phaaark about with the idle jets will ya, i'm taking notes.Dellortoman said:
cheers 8)
Dellortoman
Hero member
- Location
- Tasmania, Australia
OK. I'll send an email to Red.
Coincidentally, the dyno guy in Hobart is also called Red, a good bloke with a lot of bike knowledge and very helpful. He mostly works on Japanese bikes and has a lot of experience with Mikunis, plus a heap of Mikuni jets and other spares.
Saturdays in his workshop are a bit more informal than weekdays. It's less dealing with the public and more letting trusted clients come in and work on their own bikes using his tools and facilities. Red was running the dyno and recommending setting changes, and I was doing the spannering while he worked on another bike. There was another customer there using the tyre changing machine to do his own tyres, and a couple of others who came in for various things while I was there. I didn't know the other guys, but by lunchtime we were like old mates. There was lots of piss-taking at each others' expense, or heaping derision on each others' bikes. The Laverda was the butt of many jibes being such an old clunker among the modern stuff.
There was a young lad (about 17 or 18 I guess) there with some kind of chook chaser. When he saw me flip up the Laverda's hinged seat he said "gee, that's a good idea". He'd never seen a hinged seat before. One of the older guys reckoned he was too young to know about stuff like that. I'm too old to know any different. Don't modern bikes have hinged seats?
All in all a damn good and fun way to spend Australia Day! If I'd stayed a bit longer I would have got roped into a beer O'clock session. Someone turned up with a slab just as I was leaving. I reckon the young lad was in for an education!
Red (the Tasmanian one) is a tall guy who has a gruff manner and doesn't have much time for idiots. The rest of us in the shop were calling him "Boss". Sound familiar?
Cheers,
Cam
Coincidentally, the dyno guy in Hobart is also called Red, a good bloke with a lot of bike knowledge and very helpful. He mostly works on Japanese bikes and has a lot of experience with Mikunis, plus a heap of Mikuni jets and other spares.
Saturdays in his workshop are a bit more informal than weekdays. It's less dealing with the public and more letting trusted clients come in and work on their own bikes using his tools and facilities. Red was running the dyno and recommending setting changes, and I was doing the spannering while he worked on another bike. There was another customer there using the tyre changing machine to do his own tyres, and a couple of others who came in for various things while I was there. I didn't know the other guys, but by lunchtime we were like old mates. There was lots of piss-taking at each others' expense, or heaping derision on each others' bikes. The Laverda was the butt of many jibes being such an old clunker among the modern stuff.
There was a young lad (about 17 or 18 I guess) there with some kind of chook chaser. When he saw me flip up the Laverda's hinged seat he said "gee, that's a good idea". He'd never seen a hinged seat before. One of the older guys reckoned he was too young to know about stuff like that. I'm too old to know any different. Don't modern bikes have hinged seats?
All in all a damn good and fun way to spend Australia Day! If I'd stayed a bit longer I would have got roped into a beer O'clock session. Someone turned up with a slab just as I was leaving. I reckon the young lad was in for an education!
Red (the Tasmanian one) is a tall guy who has a gruff manner and doesn't have much time for idiots. The rest of us in the shop were calling him "Boss". Sound familiar?
Cheers,
Cam
Laverdalothar
Hero member
- Location
- Germany
Hi Cam,
do yourself a favor and in roughly 3-4 months of riding with the Mikunis, swap back to Dell'Ortos again, just for a testride right after you finished a nice run on your "home circuit" (the nicest bends around your home).
The reason I suggest that is, that my sisters husband followed my suggestion to buy an exhaust system from SR-Racing, who made the exhaust for my 1000 SFC. He was a bit calm in his reaction when I asked him about the results: "Well - it is louder than before, which I am not sure I like really and I think there is a bit more grunt in midrange. But if you ask me if it was worth the money, I am not sure..."
I talked to him last fall (after roughly 6 months of owning the exhaust) how the bike runs and if he would change back to the original system. He said that he did already, just to change to SR-Racing exhaust again after the first ride with the original system again: "it felt as if someone had stolen 10 HP from the bike. Overtaking felt sooo dangerous..."
You get used to reserves very fast and if you don't have them anymore, you miss them more than you appreciated them when you had them...
Just my 2 cents...
do yourself a favor and in roughly 3-4 months of riding with the Mikunis, swap back to Dell'Ortos again, just for a testride right after you finished a nice run on your "home circuit" (the nicest bends around your home).
The reason I suggest that is, that my sisters husband followed my suggestion to buy an exhaust system from SR-Racing, who made the exhaust for my 1000 SFC. He was a bit calm in his reaction when I asked him about the results: "Well - it is louder than before, which I am not sure I like really and I think there is a bit more grunt in midrange. But if you ask me if it was worth the money, I am not sure..."
I talked to him last fall (after roughly 6 months of owning the exhaust) how the bike runs and if he would change back to the original system. He said that he did already, just to change to SR-Racing exhaust again after the first ride with the original system again: "it felt as if someone had stolen 10 HP from the bike. Overtaking felt sooo dangerous..."
You get used to reserves very fast and if you don't have them anymore, you miss them more than you appreciated them when you had them...
Just my 2 cents...
Simonr501
Hero member
- Location
- Lympne, Kent. UK
Dellortoman said:Red (the Tasmanian one) is a tall guy who has a gruff manner and doesn't have much time for idiots. The rest of us in the shop were calling him "Boss". Sound familiar?
Cheers,
Cam
Maybe they are twins - separated at birth.
Shame one of them isn't small, he could be Red Dwarf!
D
dja981
Guest
Laverdalothar said:Hi Cam,
do yourself a favor and in roughly 3-4 months of riding with the Mikunis, swap back to Dell'Ortos again, just for a testride right after you finished a nice run on your "home circuit" (the nicest bends around your home).
The reason I suggest that is, that my sisters husband followed my suggestion to buy an exhaust system from SR-Racing, who made the exhaust for my 1000 SFC. He was a bit calm in his reaction when I asked him about the results: "Well - it is louder than before, which I am not sure I like really and I think there is a bit more grunt in midrange. But if you ask me if it was worth the money, I am not sure..."
I talked to him last fall (after roughly 6 months of owning the exhaust) how the bike runs and if he would change back to the original system. He said that he did already, just to change to SR-Racing exhaust again after the first ride with the original system again: "it felt as if someone had stolen 10 HP from the bike. Overtaking felt sooo dangerous..."
You get used to reserves very fast and if you don't have them anymore, you miss them more than you appreciated them when you had them...
Just my 2 cents...
Thats a polite way of saying "Cam your wrong"
Dave
D
dja981
Guest
Dellortoman said:
Nice report Cam, interesting results . That should upset a few people
Dave
Laverdalothar
Hero member
- Location
- Germany
Not saying Cam is wrong at all, but a) depending on the dyno used, it is hard to measure the torque gained and b) riding experience finally is subject to personal expectations and experience.