my first case reed project

[Davezilla]

Now that crank looks like it's ready for some serious service without any worries of failure. That's exactly what I was talking about in previous posts... everytime I got my crank true it would be way off, just by installing it for a test fit and removing it, it was all over the place again, and I was being as careful as possible with each install/removal.
I'm definitely going to weld my pin before the final install because I can true it up on the lathe and it moves that easily, it doesn't matter how true it is and how carefully you install it, the first time the engine is run it'll be off again because the pin lets things move way too easily.

I seriously doubt you'll have any trouble with your bottom end now, and you should have no trouble after upgrades are done... Good job

 

[mrfubs]

Thats the plan! these newer cranks come with quality crank bearings with thrust washers too. I have high hopes for this balance setting, i stuffed it with alloy to add a little more weight from how much i took off also and to keep the crank case pressure up at the same time! I drilled 2 oil holes for the main bearings on each crank half so they can breathe some what..

and you are right. These cranks are almost not even pressed together its hard to believe they dont fall apart. they leave china being 15-20 thou off its almost a guarantee. i definitely recommend welding the pin after doing any percise work to them

 

[Davezilla]

That's pretty much what I thought, I hadn't took mine apart yet, but I will if I can find a better big end bearing, and I may split it just so I can drill some oil holes and just put in a new bearing, but if I can find the bearing specs, I'll be able to get an upgraded bearing.
My other issue, and the reason for a full teardown was that I noticed a lot of side to side play... nearly 1/8" of play in my crank with it assembled. the idea was to make some thrust washers and true the crank originally, but once I saw how sloppy the fit was at the pin and all I'm definitely welding mine before I put it back together.
I got a new Dax bottom end so I can stay riding while I'm doing the work on this one but it also needs some iprovements before I can give it any type of serious power. It should stand up to my modified jug and Fred head but I'll need to raise the jug by at least 1mm or more so the piston don't hit the head and check my port timing all over again. That setup was rockin when I had it together so I want to keep the timings as close to the way I had it as possible.
I'm off to making a few cylinder base spacers now...

 

[Theon]

Another good use for street signs.
Although 1.5mm may be to much.
Did your other bottom end have a 38mm crank? is that why your needing to lift the jug?

 

[Wild Bill]

When I was building the kart motors my Son and I raced on the rod pin was swedged in place by a short tapered aluminum dowel that you would use a press to put them into the open center of the the rod pin after the crank was trued to lock all the parts from moving. Then to take the crank apart you drilled out the aluminum dowels to make it easier to get the crank apart.

 

[mech_engineer]

Looks good!!! Nice work

 

[Davezilla]

Another good use for street signs.
Although 1.5mm may be to much.
Did your other bottom end have a 38mm crank? is that why your needing to lift the jug?

here we go with the street signs again... lol...
I got sheets of 6061 T6, 2024T3, and 7075T6 in different thicknesses here at the house I make that kind of stuff out of. Just finished the stuffing plates in my first engine and got them bolted in by drilling thru the case and tapping M4x.7 threads in the discs, they'll also be assisted with JB Weld so they won't move or come loose, these started out as .090" 6061 T6 then I lathed them down to .074" to give a .010" clearance on each side.
The spacer plate I'm making now is going to be .040" 2024 T3 aluminum for the base, then I'll use a copper gasket to seal it off. I really like the copper gaskets Juice makes, I just wish his shipping was faster because all his products are top notch qualitywise.

I never measured the stroke on that crank, but all fingers are pointing to a 38mm stroke because it's exactly 1mm off from where it needs to be once a head gasket is in place.

 

[mrfubs]

well sheeeit. measure where the piston is in the bore at bdc and again at tdc. mine was 39.75 stroke so im rounding to 40. and also if how come you want to have the piston farther away from the head? it sounds like its not even at maximum squish. and if you do still want to do that i would really get a thicker head gasket instead because if you raise the jug it will mess with your timing a bit. but hey what ever floats your boat!

I just got my Dellorto 21mm clone today, very happy with how it looks and is extremely tune able. Way un comparable to the cns carb and i paid the same price..... maybe less.. it also has one extra jet i have no idea what it is maybe you can help me figure it out.

 

[mrfubs]

btw not bad pics for a phone if i may add haha

 

[Davezilla]

Ok, with the Dellorto carb, the third jet is your enrichment jet, this one controls how much extra fuel is delivered when the choke is pulled on, very similar to a real motorcycle carb in that aspect.

 

[mrfubs]

the 3rd jet in which pic? isnt the long jet the idle jet?

 

[Davezilla]

Ok... a picture can say it all here... This is why I need to add a spacer...
Most likely this one will need a thicker head gasket because the port timing is in a really good spot with it sitting on a .016" thick base, when I work on it tonight I'll put in a .040" thick shim at the base and see what the timing looks like, then I'll decide which side to shim up, as it sits it's giving me 172 deg exhaust duration with 116 degrees intake and 130 for the transfers with a 25 degree blowdown so raising the cylinder might make it too peaky with the powerband. I also have a few spare jugs just in case this won't work, but I'm going to try to get this one working on this bottom end because it was nice and strong on the other with good bottom and midrange.

 

[Davezilla]

the main jet is the one right in the middle of the carb body, then the slow jet (idle) usually sits behind the main, you can confirm this by tracing where the jet passage goes, the slow jet will go to the idle mixture screw on the side of the carb, then up to a small hole (or series of small holes) behind the throttle valve, you can check their passages by sending compressed air from one side to see where it comes out or you can use water, carb cleaner, wd40 etc with a syringe, just send the liquid into one end and see where it comes out.
The enricher jet will only pass air or liquid when the choke is activated.
Each carb can be laid out slightly different internally but typically, the main and slow jets are located so they're close to the bottom of the bowl and the enricher may be slightly higher up, but still under the fuel level in the bowl

 

[Davezilla]

on the Keihin CV40 (Harley carb) the main is in the middle with the slow right behind it, and the enricher is slightly off to the side and all 3 jets screw into the same tower casting, on yours, it looks like the main is in the middle, the slow is at the rear, and the enricher is in between, I may be wrong on the slow and the enricher because I'm not familiar with the Dellortos like I am with Mikuni, Weber, and Keihin..

 

[Davezilla]

Can you see the numbers on the smallest jet, the one with the point on the other side? from the numbers I can see, the 60 is the main, and the 20 is the slow (idle)

 

[mrfubs]

no sir 70 is the main 60 for the long jet and the pointy one is 45, i have a good idea where i need to be going from other peoples set up simular to mine. 90 main and a 50 for idle.

the pic you posted in your case i would raise the jug untill the piston is flush with the top of the cylinder.

are you running a 38mm stroke crank with a 40mm stroke piston by chance? can i see a pic of your piston i can tell in 2 seconds and if thats the case its just the matter of swapping pistons.

i post a pic of what ill be using on this build for piston and rings in a few mins

 

[mrfubs]

the piston on the left is a 40mm stroke piston the middle is a 38mm and the right is a hoca that is a perfect fit for a 40mm and uses 1mm thick rings instead of 2mm thick.

if you look closely you can see my added transferport in the back ground lol

and i found another jet too

 

[maniac57]

Lets have a link on that hoca 40mm stroke piston. I have a 40mm that needs a top end and I like the looks of that slug. Is it a direct bolt in?
What does it come from? Where can I get one? ring set? Price?

 

[mrfubs]

http://www.ebay.com/itm/70cc-PISTON...her_Vehicle_Parts&hash=item2a33d4bf5b&vxp=mtr

that is the piston, you CANNOT use the rings that come with it they are chrome plated and will destroy your cylinder in the matter of seconds.

you will have to buy Motobecane piston rings that are cast iron and not plated. they are 15$ a piece.
http://www.1977mopeds.com/motobecane-47mm-airsal-piston-ring.html


i will be getting the rings in the mail in a few days and i will verify then if they will work or not. said and done is about 65$ but off the bat your getting a casted piston that is easier on the bore due to higher silicon content and is also lighter than our forged pistons, also casted pistons are more brittle. the big factor is 1mm rings instead of 2mm rings.

even with the thicker wrist pin i think the hoca total weight is still lighter by a couple grams

 

[maniac57]

Keep us updated on this. I think there are many people who would love to hear of a better quality piston and ring set. Especially if it will work in a stock jug and bottom end