ESE's works engine tuner

[Gradella23]

Just one more small detail re the stuffer to add. Even though Im dealing with a very small carb on a big reed ( 30mm/125 reed cage ) you would think that the carb bore was the limiting factor.
Not so , the best stuffers have a 2mm smaller venturi around 10mm into the block , where normally the area would be increasing or remaining equal.
This idea may work where your carb exit is " too big " ie neck the area down into a venturi within the stuffer.

this is interesting. do you mean 2mm smaller than the carb exit (33,5) or 2 less than the nominal D (30mm at the butterfly)?

[husaberg]

Honda CR 125 2003 could hold the record for the biggest difference. For 2003 Honda made the biggest ever CR 125 reed cage ( 66 mm wide vs. 59 mm of 2002 ) with the smallest insert. Bigger air box, new carburetor 38 mm ( 36 mm 2002) huge reed cage and all this against 28 mm reed cage insert at narrowest point. Reports from testers:

"After a few hours riding the 2003 CR125R, we are happy to report that Honda has delivered a substantially improved motor, and that the chassis is just as sweet as last year. While last year’s bike required massive clutch abuse exiting corners, the ’03 model has a much broader, easier-to-use powerband. While “better breathing” might lead you to believe Honda produced a top end screamer with no low-to-mid power, this is not the case.

Indeed, the 2003 CR125R seems to pull harder from bottom to top when compared to the 2002 model (also available for our sampling at Carlsbad Raceway). For the first time in several years, Honda has a very competitive stock 125 motor to go along with its superb handling and suspension."

2004 same big 66 mm reed cage, but the insert dia. 38mm, same as carb .
From 2005 to the last 2007 CR 125, they return to narrower 59 mm reed cage with usual three petals and 38 mm insert.


Husa, other very short intake manifolds are used on the Yamaha YZ 125 from 2005 to 2022? Shorter could be to insert the carb directly to the plate that holds the reed cage.

Cheers some odd spacings put might be the go for a smaller cadge as o hasroom for redrilling


http://www.transcanimports.com/downl...%20Flanges.pdf

https://www.allensperformance.co.uk/...ormation-page/

http://jbmindustries.com/MZ_Socket_Boot.html

[wobbly]

Did a ton of dyno tests on the RS125/CR125 cage and stuffers as they fitted the TM 125MX when we had 125 National in karts ( bike engines only )
The best manifold by far was the NX4 - 000 but that has been NLA for years.
The 780 is the later model RS125 but its way too long
The angled one looses 2 Hp.

EDIT - re the reed stuffer venturi - I have no idea what would work better in your case , best to have a go with varying sizes.

[Muhr]

Tried getting a little more power from a tm mx 125 a while ago.
Where I have experienced that the most limiting thing is intake/reed.
I tried these Vforce 3,4 and 4r without any results worth mentioning.
Did as below in the end, which made a big difference for us. (from a 144cc kz kit)

[Grumph]

Muhr - not knowing what the OE setup looks like, what are the changes ? Spacer or venturi at the entry point ?

Is the angled entry a factor ?

thanks

[Muhr]

Muhr - not knowing what the OE setup looks like, what are the changes ? Spacer or venturi at the entry point ?

Is the angled entry a factor ?

thanks

A spacer was a necessary "evil" because a kz reed cage is too big to fit on an mx engine.

[husaberg]

Tried getting a little more power from a tm mx 125 a while ago.
Where I have experienced that the most limiting thing is intake/reed.
I tried these Vforce 3,4 and 4r without any results worth mentioning.
Did as below in the end, which made a big difference for us. (from a 144cc kz kit)

Did you try VF2?
My understanding is that was the one that got results at least with Hondas.
I think that came from mr Waynewright

[wobbly]

Yep , the VF2 ( original bolted together assembly ) was far superior to the later VF versions on the TM 125MX.
I think the KTM had it from the factory.

[Muhr]

Unfortunately, nothing I've tested. I also can't say that it was reed it self or an increase in crankcase volume, or maybe both. But there was a big difference

So this is the OG? https://www.ebay.ca/itm/332619174160...gAAOSwmWVaz-nT

[Gradella23]

Unfortunately, nothing I've tested. I also can't say that it was reed it self or an increase in crankcase volume, or maybe both. But there was a big difference

So this is the OG? https://www.ebay.ca/itm/332619174160...gAAOSwmWVaz-nT

hello muhr, i've seen your 50cc project while reading some pages back.. have you finally tried it? that looked nasty.

Attachment 352539Attachment 352540Attachment 352541Attachment 352542Attachment 352543

We have been running these for 7-8 years with no issues. The cages are Nylon/fiberglass, the spacer is nylon/carbon fiber. This cage is for the KX500/CR500. There are some concessions made to the build due to the material. It doesn't do well with supports so the entry of the splitters has too much of a sharp edge before it radiuises because that has been the best way to get it to build off the plate.

amazing quality. have you also experienced an improvement restricting the internal cross section instead of maintaining the carb exit cross section?
Have you tested different lenghts for the horizontal splitter? i see that this goes all the way from the base to the top of the cusp.
I even saw someone on the dutch forum (deraceheldenvanweleer.nl) hypothesizing a manifold with a continuation of the splitter, but i can't find any feedback on that.

[wobbly]

Your 1/2 moon fillers look really nice , but I now make them with no step up to the petal seal surface on the sides.
This does not apply to the end of the splitter at the reed tips , a right angle step here , on the flow bench lifts the petals higher and faster - resulting in more power on the dyno as well.
Completely counter intuitive to having a triangle divider under the petal tips - but hey its a 2T so reality doesn't match anyone's pre conceived ideas.

Also the splitter is shortened , it starts where the venturi ends , further in from the block entry face.
As we also bias the flow upward toward the piston by having asymmetric reed backups , im about to try moving the front edge of the airfoil splitter downward , too force more flow into the top pair of reed block ports.

Edit - the guys who make the UFO for Mikuni round slides also make a short splitter that divides the carb exit in 1/2 at the engine side of the slide.
This gives way better response at low throttle openings - so the idea could be extended so the reed splitter is continuous right up to the throttle slide - maybe ?

[TZ350]

.
F81M balance factor post 1.

Reciprocating weight is 372g

50% balance factor would be 186g.

And a picture of my F81M's rotary valve compared to a standard unit for anyone interested in such things.

[TZ350]

.
F81M balance factor post 2.

Ok, I see why the F81M vibrated like a basted. I had machined away so much of the counter weight there is negative balance factor.

I hung 50% of the reciprocating weight on the rod and added extra counter weight until it all balanced out.

So if I have got this right. I need to add 227g to the counter weight to achieve a balance factor of 50%.

[Grumph]

.
F81M balance factor post 2.



So if I have got this right. I need to add 227g to the counter weight to achieve a balance factor of 50%.

Or - take 227g off the pin side of the wheels.

Why 50% ? Personally I'd be going for somewhere around 60% as a starting point. Do you know the OE balance factor ?

[F5 Dave]

Can't help you there but your gudgeon pin looks dreadful. Hope that's an old scrap one.