Making a Cyclone 440 from a 340

[jdxrobin]

Hello everyone...
It's been way too long since I have visited.
I have a question. My boy has a great running 1976 340 cyclone that I have rebuilt everything on but being a typical guy I think I can make it better!
I have a 440 Kioritz that needs the crank rebuilt, but everything else seems OK.
My question is, can I just change the jugs and pistons from the 440 on to the 340 and voila...Robins boy has a 440( )?
I have the complete exhaust from the 440, but it looks pretty close to the 340 so I am thinking I don't have to worry about that
What about the ignition? As for carb settings (or carbs ...another topic!),I would change to the 440 settings, etc.
Also, it's a little off topic, but does anyone have a decent Cyclone chassis around Minneapolis? I would be willing to make a road trip if necessary.
I call the boys sled the road warrior...yep, its pretty bad, but she's a runner!
Thanks for your help.

Robin

[ihengineer76]

You are correct. The top ends of the engine will swap, and ignition and exhaust will be the same. The carbs will be different. The clutching will also be different. A parts manual will help you a lot with seeing what needs to be done.

[harleysportster]

Is your 440 a 1976 as well? If not, use the exhaust that came with it. The '76 exhuast pipe is tuned differently than the 77/78's. The carb specs are different for 77/78 also.
http://www.jdsleds.com/community/viewto ... ?f=5&t=368
The only other thing not mentioned is the chain case gears are slightly different but you can use the 340 gears. The top end suffers slightly.

[jdxrobin]

Thanks Guys for the responses...
I think I have all the parts I need to make a runner.
Robin

[jdxrobin]

OK...I purchased new wrist pins and when I got them home they were almost a 1/4" too long compared to the ones I pulled out of my 440!
In looking at their part number as well as the part number from Dennis Kirk (they match), they have given me the correct ones
The wrist pins I have are 2.207 (56mm) long and the replacements he says I should have are 2.437 (62mm) long.
I am somewhat curious as to why both Dennis Kirk as well as Pats small engine both have the wrong length listed.
Any thoughts?

Robin

[harleysportster]

Robin,
I am not sure of the part number you ordered but here is the correct number from Dennis Kirk. I have used these. The size is 18 x 2.435 mm.
https://www.denniskirk.com/parts-unlimi ... /14450.sku

[jdxrobin]

And that is the length I got from Pat's...it was way too long!
Is it possible that the pistons were switched in the engine I have? I looked in the DK catalog and the length I have seems to correspond to a couple of Arctic Cat's and a couple of Polaris'? The pistons seem to be factory. One thing though...not sure if it is significant...the arrows in the top of the 440 pistons do not point straight forward to the exhaust port like the 340 I have. They both point approximately 30 degrees off to the sides. I did think that was a little odd.
In measuring the pistons (they measure 66mm like they should), the only way these pins would fit is if I left the circlips off. As the rods don't have a press fit for the pin...I'm thinking no!
To be sure, I can just purchase the right length from Kimpex. or Wiseco, but now curiousity is getting the better of me and I would like to find out why the right pins are wrong...
Any info would help?

Robin

[harleysportster]

The arrows do not point directly forward but to the outside at an angle once installed on the rod. If the arrows on your pistons pointy forward once installed, you have the wrong pistons.

[jdxrobin]

Well, that is what they do so they must be factory.
I guess I will just purchase some shorter pins and get on with life...
Robin

[jdxrobin]

Alright everyone!
I got the right Wiseco wristpins, splurged and bought 15 gallons of part cleaner for my new harbor freight parts washer (everyone...take this to heart...It's not cheap, but go to Tractor Supply and get PSC-1000 cleaner! It worked so well I was looking for things to clean! I can't recommend it highly enough ), cleaned everything, rebuilt the carb (Mikuni 34-124...new 420 main jet, 30 pilot jet, P-2 needle jet), put it all back together (125 and 130 compression in the cylinders )got new NGK BR10ES plugs, and second pull, she popped !
This was way too easy though...
It would not run with the choke so I had the boy pull while I worked the throttle (no choke). She started up and ran but would not idle. I went back to the manuals, adjusted everything again to the initial start-up points for the choke cable, throttle slide, throttle cable, and air screw (2 turns out) and she ran pretty rough...still no idle. I pulled the plugs after running it for a few minutes at approx. 2200 rpm's and they were pretty wet, but did not have a strong gas smell.
I screwed the throttle stop screw all the way in and it would not run without the throttle pressure
...any thoughts?

Robin

[harleysportster]

Robin,
You never mentioned what year the 440 cylinders and head are? There is a difference between 76-77/78. Also, what jet needle is in the carb?

[jdxrobin]

Well,
The needle is a 6FL14 on the third groove, but after thinking about it, I tried one more thing.
In the interest of performance (lighter weight makes thing faster right?), I changed the throttle slide from the original heavy chrome plated brass unit to a lightweight aluminum one...just for kicks I changed it back.
...Runs like a top !!!
OMG...one pull with no choke and it idles at 2000 rpm all day long and does not run rich!
Any thoughts as to why it worked this way?
I am so excited I can't stand it !

Robin

[harleysportster]

Way to go.
The heavy chrome slide is the correct slide. The aluminum on you had may have had a different cut-out angle.

[JDT]

Just what I was thinking.

[jdxrobin]

Both of the slides were a 2.0.
All I know is I had my youngest daughter come out and start it (110 lbs soaking wet...the best test I could think of) and on the first pull it started and idled perfectly.
...I'm ready!
Thanks for your help.
Robin