So recenty I whent for a ride  and when I was on the highway the bike started to chooke up ..and a minute latter I was on the side of the road ....  I cheked my plugs and ......  



2 monts ago,  I took the Hayne's book and put everything to specs......that was the result

I knew I add a main jet problem.....  from 3/4 of the trottle to the top 

So i've decided to move some thing's in the carb whit what  I've learned about carbs over the years  this was the result.....



On the left my setup

I've put the main jet  132.5 just over the needle and I left the  the other "main jet" 140 where it was

On thre rigt side it's the EOM setup . The "starter jet" 70 and the main jet is 140 but there no jet over the needle.



I've observe at least 20 % increase in performance fot 2 reason...

- the hole over the needle is not block anymore becose the main jet is direcly over the needle ...... so there no devation of the gas ..
-well...bigger jets =more performance

For now the plugs hare cofee brown.... and the last 3/4 of the trottle works like a charm

I'm glad you know what's going on. Carbs still confuse me, that's why I live near Koko64

Carbs, still black magic to me . . .

Tank's 

It looks better 



I intend to share a little bit of knowledge in this tread 

I'm also shure that I will learn some things too 

Very interesting. I understand what you are doing, but never bothered in the end, pursuing other mods instead. The idea of lining up the circuits seems common to all performance carbs, and simpler. Makes you wonder why they didn't want to do it this way from the start. Certainly a difference between many CV carbs and Flatslide carbs. Emissions? I don't know.
Very cool. Your talents never cease to impress!
I was just talking to someone about some Honda race carbs that were actually CV carbs used on Paris/Dakar Cagiva Elefants. (Honda quietly helped Cagiva against Yamaha it's said). From the look of the shape of the float bowls, they had this mod.

I would like to see some dry carbon on the outer rim of the plug though. Also look deep into the plug with an LED light to check the colour down near the base where the porcelain meets the bottom of the plug. Modern fuels seem to require looking at more than just the upper porcelain to be confident. A little on the rich side wouldn't hurt an air cooled motor.

That mod would have as much to do with response as it would with peak power and economy/efficiency. The fuel may atomize better and be delivered more directly.

When I looked at modifying CV carbs for others the labour cost was starting to stretch towards new FCRs or similar to Mikuni TM flatslides if one went too far. Doin it for your own bike is worth it if you know what you are doing and want to save $$$.  You clearly know what you are doing. The bang for buck doing yourself is great rather spending 1K on FCRs.
I just jet them and radius the bell mouth and slide face to reduce turbulence and slide flutter. That's what we did on Harleys went they went to CV carbs in the mid '80s. I  think the equivalent Keihin CV carb is a better carb. It came in 40+mm sizes and some came with accelerator pumps for big twins. The Harley version came in 40mm pumper form and it could be possible to use two on short manifolds if anyone wants to try it!
Not that I'm tempting you Isabelle

Quote from: koko64 on June 22, 2014, 08:15:50 PM
Very interesting. I understand what you are doing, but never bothered in the end, pursuing other mods instead. The idea of lining up the circuits seems common to all performance carbs, and simpler. Makes you wonder why they didn't want to do it this way from the start. Certainly a difference between many CV carbs and Flatslide carbs. Emissions? I don't know.
Very cool. Your talents never cease to impress!
I was just talking to someone about some Honda race carbs that were actually CV carbs used on Paris/Dakar Cagiva Elefants. (Honda quietly helped Cagiva against Yamaha it's said). From the look of the shape of the float bowls, they had this mod.

Tanks   ...  that coffee brown plug was only after a 10 km ride...... tomorow  I'm riding to work (60km)  so the color of the plug will be more precisse....

My boyfriend told me the only time he saw carbs whit the mukini EOM setings. It was on snowmobiles from the 70'
I have a 1995 monster ...from the cagiva era ...  

Hello Isabelle.
Been thinking and have some questions. Very curious about this.

How does the starter circuit work with the starter jet (70) removed?
Since you are running two main jets, is one like a power jet? How does it work?
I understand your objective to put the main jet under the needle jet so they are all in line, so why two main jets?  
I have heard of a mod with 132 main jets, why isn't the bigger main jet under the needle jet, and keep the starter jet?  

You caused carburettor mayhem in my mind!

I should have asked this question first. The first spark plug was rich, so was there flooding or too large a main jet, too high needle, worn needle jet, etc?

Quote from: ducatigirl100 on June 22, 2014, 09:30:27 PM
I have a 1995 monster ...from the cagiva era ...  

Me too!

Quote from: koko64 on June 23, 2014, 02:25:19 PM
Hello Isabelle.
Been thinking and have some questions. Very curious about this.

How does the starter circuit work with the starter jet (70) removed?
Since you are running two main jets, is one like a power jet? How does it work?
I understand your objective to put the main jet under the needle jet so they are all in line, so why two main jets?  
I have heard of a mod with 132 main jets, why isn't the bigger main jet under the needle jet, and keep the starter jet?  

You caused carburettor mayhem in my mind!

I'll response in 3 different reply's

1- th carb work like VM or  a TM .....  the 70 "starter jet" was only one more step to give gas .....  less effective

The design of the mukini bdst 38 is an old desing that is not commonly use anymore

Now  the starter circuit work only whit the pilot jet

2- before the main jet was effective in the last 3/4 to full throte.  

Now by having  2 main jets they starts to give  gas from 1/2 to full throtle

3- I've put a 132.5 jet under the needle because it was what I add  . I have to get some 140 main jet this week

As for the "starter jet " it was no use in the new desing since I have 2 main jets so I use the "bolt" to block the hole it was in forcing the gas to go in the 2 main jets



These's are the essentials of what I did but I must admit that my boyfriend help me  to sort it out . I add the basic idea but I asked him questions for at least 2 week ...nice couple bedtime conversation  whe dont talk about kids, finance or sophing.... yepp ... carb discusion before going to sleep ...lol

My boyfriend is a ex AMA  motocross racer and he whon a couple of race's on the track too....
And he make  great coffee