my first case reed project

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mrfubs

Member
Jun 13, 2013
306
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michigan
so far iv got it down pretty decent. i was looking at my bike one day thinking how i could get my reed block into the case for full advantage of the reed valve system. A couple hours later with a dremel i have it all mounted to the case and looking decent.

My plans:

-getting the crank trued and ill do my own balancing work
-26mm mikuni kx65 carb.
-hoca piston with motobecane rings
-twin plug fred head with compression release
-extensive porting work
-stuffing the crank
-centrifugal clutch
-maybe use a parmakit 75cc cylinder with 7 ports
-yz80 exhaust pipe
-32t sprocket
-huffy cranbrook
-hydraulic brakes
-suspension fork



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i might try this exhaust

http://www.ebay.com/itm/151256949245?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

or this one that i currently have on my current bike

http://www.ebay.com/itm/03-YZ85-yz-...Parts_Accessories&hash=item3cddd885d6&vxp=mtr

Here the carb

http://www.ebay.com/itm/19061826777...em=&sspagename=ADME:X:AAQ:MOTORS:1123&vxp=mtr

or this carb

http://www.ebay.com/itm/38044214606...em=&sspagename=ADME:X:AAQ:MOTORS:1123&vxp=mtr

Piston rings

http://www.1977mopeds.com/motobecane-47mm-airsal-piston-ring.html
 

Theon

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Jan 20, 2014
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I think the 26mm carb a little big, but otherwise nice work.
Although the 26mm is likely the OD of the motor side of the carb looking at the adds and that would make it a more reasonable 21mm bore.
 
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Davezilla

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Mar 15, 2014
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Nice work on the cutting to make the reed box fit.
yeah, 26mm may be a bit excessive, but if you go with a 21mm Mikuni you'll be doing great.
For the pipe, any of the Japanese dirtbike pipes will get you more power, same as the pocketbike fatty pipe you're looking at, it'll work good and make good power but needs to be modified... I'm running a modified cag pocketbike pipe on mine and it did make a huge difference over stock, and with some mild porting the bike is nice and strong. I do have a KTM 65 pipe on the way too :)

You do have a really good parts list for this build too... I'll be following this post
 

mrfubs

Member
Jun 13, 2013
306
12
18
michigan
I will be making my own reed inlet with a tube that will fit a 26mm carb, the one on it now will only fit a 18mm carb. The old saying if your carb is bigger than the inlet of the engine then there is no gains to be made.

Dave over at arrows uses a 26mm mikuni on his case reed engine.

The onlything im not 100% sure of is how to calculate degrees when advancing ports. Any help with that would be greatly appriciated.
 

mech_engineer

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Mar 3, 2014
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the time area is a combination of degree and port area for "x" rpm is very complicated to try it without read more about it. you have two ways of doing it increase area or increase duration. first try to increase the exhaust port to 62% fo the 47mm or .62*47= 29mm port wide do not increase the port upwards only to the sides. then test your engine if want more power increase the port upwards 1mm at a time 1mm makes a huge diference in durantion so be carefull
 

Theon

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Jan 20, 2014
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I use a $1 protractor with a an 8mm hole mounted to the mag rotor as a degree wheel. Set it to TDC with a dial guage or by doing a squish test.
Then it is easy to get your port timing spot on, by adjusting transfer port height with base gasket, then blow down by adjusting exhaust height.
 

Theon

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Jan 20, 2014
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What revs are you after?, and how much low down are you willing to sacrifice for top end?
But yes reading and making your own choices on port timing is the go.
But I'd be looking around 120 ATDC for transfers, for top end, and around 102-105 ATDC for exhaust. But experimenting with different combinations of set up is where it's at.
 

mech_engineer

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Mar 3, 2014
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you need to know how much revs you want and type of power band torque faster acceleration but limit max speed or hp slower acceleration and max speed(only for flat roads not for hills)
 

mrfubs

Member
Jun 13, 2013
306
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michigan
with my current build i was pushing 8600rpm with the exhaust port slightly advanced and the piston notched with a un trued half ass balanced crank. with this new engine im looking for 10+k rpm with this new piston and ring setup if the crank can handle it the piston and rings along with the cyl wall will as well.

i have a lot of home work to do as far as transfers and exhaust advancement goes.

i not sure if i want to run a 21mm carb i have a feeling it will be restricted, fred uses a 21mm carb on a cylinder induction engine. with a case reed induction and a well ported cylinder along with a good flowing exhaust setup it will need a lot more fuel, heck a kx65 uses a 26-28m carb
 

Theon

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Jan 20, 2014
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Piston port needs a bigger carb than reeds as the intake duration is less.
Larger Carb will adversely affect low down torque, which is more important when there is only one gear ratio.

Surface speed of piston with 40mm stroke is starting to be stretched above 10 000 RPM.
Kawasaki make very good motors, these are sh*t, So not a very good comparison.
 

mrfubs

Member
Jun 13, 2013
306
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michigan
you make a very good point. even if i had the crank torn apart and had quality needle bearing installed and a beefier connecting rod pin with a true and balanced crank there may be some hope but i would say 10k would be the most then huh.

what i dont understand is why does dave use and sell his case reed engine with a 26mm carb? he must have pretty good results? i just wanna be double sure what carb i buy so i dont have so much junk lying around yaknow. but then again im leaning pretty far towards the dellorto 21mm clone, do the clones perform just as well? im also going to do the lever choke conversion

http://www.ebay.com/itm/03-YZ85-yz-...Parts_Accessories&hash=item3cddd885d6&vxp=mtr
 
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Theon

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Jan 20, 2014
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is 26mm the OD or ID? of carb?
like Mech' said, 3.2 cm2 max inlet.
21mm Carb gives 3.4cm2
Or at least that's what I worked out.
I've had my previous 'race' motor doing 80 Km/hr at 9500 RPM on a 16mm carb and piston port.
I personally don't actually wan't to go any faster than this on a push bike, but each to there own.
For me this project is about getting a wider power band, and getting to 80 K quicker, and possibly with a few less revs, by running a 32-34t over the 36t that I have been running.
So I'm looking for around 9000 max revs, and having a little up my sleeve at 80 K (50 MPH).
 

Davezilla

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Mar 15, 2014
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The engines Dave sells with the 26mm carb do work for what they're built for... al out racing. The problem with these setups tho is if you do this for street use you'll see that your engine will like full throttle or no throttle making it less ridable with a lot less low end manners. They do their job very well when you can keep them reved up where the power is at, but there's not much power left down low where you'll be spending most your time if you plan on riding it on the streets a lot. These engines do rock when they're in their power band tho.
The smaller 21mm carb will give you better signal to your carb for better part throttle and lower rpm use allowing it to be more streetable and still have way more power than you had before.
 

mrfubs

Member
Jun 13, 2013
306
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michigan
my current piston port bike did 48 mph with a 36t and that was sketchy with the frame i had and the small tires, im going with a longer reinforced frame and 3.0 with 3.0 wide tires.

when i ride my bike im never really half or part throttle im all out everytime. im going to try the 21mm dellorto clone i can alway upgrade. but i do need to know if the clones do not perform as well as the real dellorto's and hopefully i have better luck with that carb than i had with the CNS that im currently running now.

im going to buy a new 40mm stroke crank, thankfully the new ones have thrush washers and 3 oil holes on each end hopefully theyre more true but my guess is they will be just as sloppy.

btw if you all are interested this is a video of a small burnout of my current bike, not much smoke sense the tires shreded more than they smoked.

https://www.youtube.com/watch?v=0zLrf0AVMAM
 

Davezilla

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Mar 15, 2014
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The clones should be ok, and should be an improvement over the CNS carbs as far as reliability... I've had nothing but trouble with the Speed carb mine came with... mainly the built in fuel valve that likes to shed tiny pieces of rubber that finds it's way into my main jet and fuel inlet. The lack of a slow circuit also makes tuning sketchy at best.

I'll be experimenting with a floatless Tillotson carb next time I put mine back together since it can be tuned by adjusting the low and high speed settings with no jets to change out, and it can be oriented as a side draft or a 45 degree down draft, eliminating any bends in the induction path. We can use the Walbro or Tillotson carbs on these engines pretty easily by fabbing up an adapter plate and these carbs come in sizes ranging from under 10mm all the way up to 42mm and everything in between so there's plenty of carb selection... I may even put one of those 42mm Tilly's on my Harley Sportster as an upgrade to the stock 40mm Keihin... These carbs are usually standard on chainsaws and weed whackers since they don't have to be level, but they have also done really well on racing karts, snowmobiles, and other high performance 2 strokes in the 30 to 350cc range
 

mrfubs

Member
Jun 13, 2013
306
12
18
michigan
thats actually a really great idear for a carb it seem as it would be a lot easier to tune than a carb with a float. i might look into that my self now that you bring that up.

Thankfully a few gas stations by me sell fuel with out ethanol, that crap brittle's the sht out fuel lines and especially rubber diaphragms in those types of carbs.
If the high low tuning is the only thing you have to do to tune your engine in it almost seems too good to be true minus the small factor of mounting it