Ultima 127 Mods.

[Durwood]

The Jr dragster guys have some cool stuff for Mik's, and fuel pumps here's one of many.


http://www.blossomracingengines.com/partslist.php?main=Carburetor%20Parts&page=16

I like the deep bowl ..JMO

Craw's racing, JR Racecars to name a couple more.

[Admiral Akbar]

Here's my solution guys.

pn. DF44-211  Mikuni vacuum pump. 14 liters / hour
pn. 786-27001-2.3 smaller float bowl valve.

I also run a deep style drain nut with extender for the main.
It makes no difference if you make the bowl larger, your hamstrung by the delivery amount via gravity feed.
The solution is to force feed the bowl, run the main as deep into the bowl as you can.
The smaller valve is needed to restrict the gas volume being pumped.
You will have a full bowl all the time without it pumping onto the ground at idle.
The pump is small enough to hide under the tank and requires no maintenance.
You definitely will feel the difference on the top end pull.

There are 2 issues with the bigger miks.. One, they don't have emulsion tubes and two, the float bowl is too small.. Both lead problems due to areation of fuel in the fuel system. An emulsion tube will help to stabilize fuel flow and a deeper bowl will help to control then fuel level.. Remember Minton helped with the design..   Increasing pressure in the fuel system is a bandaid fix.. Ever wonder why the SnS carbs don't have this problem?? 

Max

[build it]

I thought S&S carbs do have that problem? I know Ron Dicky posted about several years back.


*clarity of message

[Nowhereman]

Here's my solution guys.

pn. DF44-211  Mikuni vacuum pump. 14 liters / hour
pn. 786-27001-2.3 smaller float bowl valve.

I also run a deep style drain nut with extender for the main.
It makes no difference if you make the bowl larger, your hamstrung by the delivery amount via gravity feed.
The solution is to force feed the bowl, run the main as deep into the bowl as you can.
The smaller valve is needed to restrict the gas volume being pumped.
You will have a full bowl all the time without it pumping onto the ground at idle.
The pump is small enough to hide under the tank and requires no maintenance.
You definitely will feel the difference on the top end pull.

There are 2 issues with the bigger miks.. One, they don't have emulsion tubes and two, the float bowl is too small.. Both lead problems due to areation of fuel in the fuel system. An emulsion tube will help to stabilize fuel flow and a deeper bowl will help to control then fuel level.. Remember Minton helped with the design..   Increasing pressure in the fuel system is a bandaid fix.. Ever wonder why the SnS carbs don't have this problem?? 

Max

They also run like "Potty mouth".
One of the worst street carbs ever.
All those mods just to make em run decent?

Never ever have I seen or heard of aireation issues with Miks.
Pumps have been used for years and are SO stuff for racing snowmobiles.
Forced fed bowls work great for racing applications where large amounts of fuel are needed... IE. large cube motors.
Normal street stuff doesn't need it but if your up there in rpm with large cubes, it is required.

[build it]

Related thread: http://harleytechtalk.com/htt/index.php/topic,19641.25.html

[Admiral Akbar]

They also run like "Potty mouth".
One of the worst street carbs ever.
All those mods just to make em run decent?

Never ever have I seen or heard of aireation issues with Miks.
Pumps have been used for years and are SO stuff for racing snowmobiles.
Forced fed bowls work great for racing applications where large amounts of fuel are needed... IE. large cube motors.
Normal street stuff doesn't need it but if your up there in rpm with large cubes, it is required.

Funny I've had more problems with Mikuni's than with SnS carbs.. Motor I got pulls 144/146 with the HSR48 without any sign of leanness at WOT but wouldn't cruise at a constant speed with an occasional cough / stumble.. Going up on the needle and needle jet made it better.. Funny but rubber mounting the air cleaner allowed me to drop the needle and needjet..The bowl baffle posted in the link also helped. Doing things to reduce vibration help to the point where the I dropped the needle and needle jet even more.. WOT the thing never misses a beat.. 

Max


Add also had a venting problem with the gas cap early on.. Can't blame that on the carb tho.

Max

[speed limit]

Max I made my own spacer like most other do dads, I`m a Mikuni guy with a hi flow pet cock and 5/16 fuel line there is no way your going to exceed the demand of gravity heck a even a stock petcock will drain a tank in 10 minutes you think you can run through a tank that quick not even at wot

[speed limit]

Well I tore into my engine this week I had suspected blow by because my oil was turning dark prematurely, I found a 1" section of the bottom piston ring land broken off the rear, both pistons had worn out wrist pin bores, mild scuffing on the piston skirts same with cylinder walls, it looks like there is plenty of material on the cylinder liners so I`m going ahead with my plan to bore them + .062 and install wiesco 4.312 pistons with +6cc domes this will give me a 131 @ best I can figure around 11:1 comp. thinking of maybe a cam change its got a S&S 640 now my question is do you guys think there is enough difference between the ss 640, red shift 647, t man 662 or wood 9f to discern ?

[Nowhereman]

Well I tore into my engine this week I had suspected blow by because my oil was turning dark prematurely, I found a 1" section of the bottom piston ring land broken off the rear, both pistons had worn out wrist pin bores, mild scuffing on the piston skirts same with cylinder walls, it looks like there is plenty of material on the cylinder liners so I`m going ahead with my plan to bore them + .062 and install wiesco 4.312 pistons with +6cc domes this will give me a 131 @ best I can figure around 11:1 comp. thinking of maybe a cam change its got a S&S 640 now my question is do you guys think there is enough difference between the ss 640, red shift 647, t man 662 or wood 9f to discern ?

Could not say but, I bet the T man or the Woods unit will make more valve train noise.
Just make sure you do the math with those bump sticks to insure a good cylinder pressure is achievable.

[speed limit]

Yeah I`ve run the 9F in the past didn't mind the noise but it seemed to be hard on front exhaust lifters

[HD/Wrench]

the 640 at that compression and CI will work very well. Keep valve train noise and wear well under the curve vs over.. Look forward to seeing the tq curve on that monster.. I have a dyno sheet of the 140 engine in the files. Will have to see if I can dig it out.

[speed limit]

well my 4 1/2 stroke X 4 5/16 Ultima 131 is together, starts easy and runs as quiet as a stocker put about 50 miles on it last night in the rain

[Nowhereman]

Should be a torque monster and they are fun.

[speed limit]

"Houston we have a problem" fired the bike up so I could get a few more easy miles in let it fast idle 1800 rpm for a minute or two eased out my driveway and down the road shifted into 2nd @ 2000 rpm and bike shut`s off just like I bumped  the kill switch, pulled over and tried to restart and noticed that the motor spun over real easy anyway got It home checked things out and no its not a electrical problem the right side pinion shaft broke off ouch!  lower end has 60,000 miles on it, do you guys think the increase in compression had anything to do with this or was it just time and metal fatigue ?

[Nowhereman]

A fresh top end puts strain on a tired bottom but 60k is not that much.
This one will be interesting to  see.
My bet is that you got a seizure in one of the cylinders.
Maybe partial.

[speed limit]

Just puled the engine, crank was shot I can get 1/8'' movement from side 2 side, I`ll split the cases tomorrow and see just what happened, I think I will replace the crank with a 4 5/8 with the 4 5/16 pistons it will be a 135"

[Nowhereman]

[speed limit]

Got the cases split bearings on left side were toast, at least the cases are good 

[Nowhereman]

Man u musta beat the snot out of that thing.
Should of gotten at least 100k out of the bottom end.

[speed limit]

8 years 60,000 miles not bad for a motor making 150 ft.lbs.of torque its seen all types of duty from racing to touring, I think I hurt it when riding with a Yamaha Royal Star across Texas we rode through a couple tanks of gas at speeds above 100 mph

[speed limit]

Got it back together S&S 4 5/8 crank JE 4 5/16 + 6 mil dome pistons 640 cam std stage 4  oval port heads mikuni 48 jims roller rockers, I will get it into the frame this week should be a runner

[Nowhereman]

That pump is gonna be an ape raper when it's fired up.
Enjoy it.

[speed limit]

Back on the road this thing is a hoot   

[strokerjlk]

Back on the road this thing is a hoot   

bet it is

[Classic Beast]

It's been a while since you got this up and running, any more problems? My 127 has about 30,000 miles on it so far no problems but I am getting what sounds like either piston slap or piston pin noise. I switched the carb over to a 51mm SE CV carb and I find it works better than the mikuni or the S&S to fit it I just machined down the S&S manifold.