78 Cyclone POOR MID RANGE

78CYCLONEPJ · Post by **78CYCLONEPJ** » Tue Jan 01, 2013 6:20 pm

HI Everyone I'm a returning member to this site. Quick back ground...... I have a 78 Cyclone w/KEC 340 22/B I snocross this sled in a local Vintage series. I am up against primarily 440cc machines because that is the class limit. I do however do very well. The machine is basically stock, I have had the engine bored out to fit new 40 over pistons. The airbox has been replaced by UNI foam filter. The stock exhaust is still in use. When the engine was apart new crank seals were installed intake and exhaust were polished. After running the sled the belly pan under the manifold/exhaust joint there was a thick black mass of unburnt fuel/oil mixture. So I adjusted the timing. Just by trial and error. Seems better now. The sled starts easy and idles fine, throtlle reponse up to 3000/3500rpm seems good but around 4000 to 5500rpm it gets boggy. After it slowly clears that rpm range it runs well at full throtlle. I have played with various carb settings (carb is stock no jetting). Going crazy trying different combos. Need a carb expert to confirm whether or not I need new jetting and roughly what sizes to get.
Thanks
PJ

harleysportster · Post by **harleysportster** » Tue Jan 01, 2013 7:03 pm

I am no expert but you need to check the plugs for proper color of "brown card-board" during a high speed run and shut off the engine. The card-board color will tell you if the main jet is correct. If it is on the lighter side, it's lean. if it's on the darker/ blacker side, it's rich. The mid range problem can be adjusted by changing the position of the "E-clip" of the carb slide. Moving the clip down will richen up and moving the clip up will lean it out.
Good luck,

JDT · Post by **JDT** » Tue Jan 01, 2013 7:21 pm

You said no jetting/stock carb.

What jets are actually in it?

harleysportster · Post by **harleysportster** » Tue Jan 01, 2013 7:52 pm

JDT wrote:You said no jetting/stock carb.

What jets are actually in it?

That's a good point Tod !

78CYCLONEPJ · Post by **78CYCLONEPJ** » Tue Jan 01, 2013 8:30 pm

Thanks for quick response. The plugs look OK, but now that you mention it Champion QN1 plugs are no longer available. I have NGK Iridium plugs BR8EIX in the sled now what is the recommended plug? I will check the jetting tomorrow and post the numbers. When I bought the foam filter (to elminate the air box) it was recommended that I change my jetting. True or False? Does the fact that I have oversized pistons matter (jetting)? Sorry guys I now it's a lot of questions, carbs are not my thing, I do understand how each part of VM 34 works and what it does, I just never had to play with jetting before.
Thanks again
ChasingCheckers20
PJ

harleysportster · Post by **harleysportster** » Tue Jan 01, 2013 8:43 pm

78CYCLONEPJ wrote:Thanks for quick response. The plugs look OK, but now that you mention it Champion QN1 plugs are no longer available. I have NGK Iridium plugs BR8EIX in the sled now what is the recommended plug? I will check the jetting tomorrow and post the numbers. When I bought the foam filter (to elminate the air box) it was recommended that I change my jetting. True or False? Does the fact that I have oversized pistons matter (jetting)? Sorry guys I now it's a lot of questions, carbs are not my thing, I do understand how each part of VM 34 works and what it does, I just never had to play with jetting before.
Thanks again
ChasingCheckers20
PJ

PJ,
I am a believer in running a stock airbox but since the Cyclone does not use a Power-Jet carb, you can remove it but you will need to adjust the jetting accordingly. There is no magic number once the air box is removed, it becomes trial & error. It would be much simpler to get a stock box and put it back together the way it was meant to be. I personally have a 76 440 and a 78 440 Cyclone with total stock jetting and they run fine. Having oversize pistons does not create that much difference. Since oem stock jetting is usually on the rich side to begin with, running the stock jetting should still be fine but the test would be to check the plugs as explained earlier.

harleysportster · Post by **harleysportster** » Tue Jan 01, 2013 8:47 pm

Here is a link tothe carb settings.
http://www.jdsleds.com/community/viewto ... ?f=5&t=368

johnnycyclone · Post by **johnnycyclone** » Thu Jan 03, 2013 6:08 pm

I'm not an expert either, but my experience with foam filters has taught me, less restriction, means more air, which means you are going to need more fuel. I have uni pods on my 77 Liquifire 440, stock main jets should be 220's. My first plug check showed no color, which means I was way lean. Right now I am at 260 on the PTO, and 250 on the mag side and am showing a light tan. Just curious on how you are checking your plugs? The correct way to check them is to do a high speed run, and to shut the engine off while at speed, so take a wrench with you when you make your run. If you run the engine at anything below top speed, like on the way back to the garage, before checking your plugs you will get faulty readings. This may be obvious to most, but sometimes it's misunderstood. Once you get the main set then you can play with the needle jet/jet needle and see if you can help your mid range. Is it possible this could be a clutching issue? Again, not an expert, just asking the question. Also, did this sled run great before, if so, what has changed?

Terre

78CYCLONEPJ · Post by **78CYCLONEPJ** » Sat Jan 05, 2013 2:50 am

OK all very good info, thanks a bunch!!! I found my old air box. the reason I took it off two years ago was that the metal mess was starting to rust and it was getting into the carb, so I replaced that with the foam. Thought was, if it could breathe better it would run better....not so much. I sanded the mess down and gave it a light spray of rust paint, threw it all back together, returned all carb settings back to factory. Took it for a run, much better just a little fat still between 4 & 5K rpm so I pulled the needle and raised the clip setting to the 2nd one from the top. BEAUTIFUL no flat spot. It was a cool day day around -6 or -7 Cel. If I run the sled on a day that is warmer, say around 0 deg Cel what if anything will I notice and how should I correct it?
As I mentioned at the beginning I run this sled at snocross events in my area and I am typically up against 440cc machines. Because the tracks are short 440s don't have a huge advantage it mostly comes down to driver ability/balls. Will using the foam filter and re-jetting give me more output? What about pipe modifcations?
My secondary clutch has settings 1 - 4, factory is 2. If I move the spring to position 1 then the engine should reach max rpm sooner, correct? As I drove down the road it took some distance to reach my max speed. The track straight a way may only be 60-70 yards so I am looking to get there as soon as possilbe.
Thanks again guys
PJ

harleysportster · Post by **harleysportster** » Sat Jan 05, 2013 2:29 pm

78CYCLONEPJ wrote:OK all very good info, thanks a bunch!!! I found my old air box. the reason I took it off two years ago was that the metal mess was starting to rust and it was getting into the carb, so I replaced that with the foam. Thought was, if it could breathe better it would run better....not so much. I sanded the mess down and gave it a light spray of rust paint, threw it all back together, returned all carb settings back to factory. Took it for a run, much better just a little fat still between 4 & 5K rpm so I pulled the needle and raised the clip setting to the 2nd one from the top. BEAUTIFUL no flat spot. It was a cool day day around -6 or -7 Cel. If I run the sled on a day that is warmer, say around 0 deg Cel what if anything will I notice and how should I correct it?
As I mentioned at the beginning I run this sled at snocross events in my area and I am typically up against 440cc machines. Because the tracks are short 440s don't have a huge advantage it mostly comes down to driver ability/balls. Will using the foam filter and re-jetting give me more output? What about pipe modifcations?
My secondary clutch has settings 1 - 4, factory is 2. If I move the spring to position 1 then the engine should reach max rpm sooner, correct? As I drove down the road it took some distance to reach my max speed. The track straight a way may only be 60-70 yards so I am looking to get there as soon as possilbe.
Thanks again guys
PJ

The air box was installed originally for noise reduction. Removing it and rejetting, marginal increase in power.
There maybe aftermarket pipes available which may give a power increase but usually also require porting.
Increasing the spring pressure in the secondary, increases the engine RPM and also increases the backshifting of the clutch.
what color main spring do you have in the primary, black or silver? What degree cam is in the secondary, 38 or 44?

78CYCLONEPJ · Post by **78CYCLONEPJ** » Sat Jan 25, 2014 12:47 pm

I'M BACK more excited then ever. I have done some digging into some other mid range / top speed issues. Something that I forgot about was the fact the when I first bought this Cyclone the primary was pooched. I bought another 102C from a used part dealer. At the time I did not know the 102C came with different setups and bolted it on. So I have been running all this time with a light blue spring instead of the silver one. I changed out the spring and made big gains. My question now is what is the correct arm/cam weight for my 102C. Motor is a KEC 340/22.

harleysportster · Post by **harleysportster** » Sun Jan 26, 2014 8:44 pm

Not knowing your elevation, all the info is in here...
http://www.vintagesnow.com/John_Deere_f ... one_SM.pdf

78 Cyclone POOR MID RANGE

78 Cyclone POOR MID RANGE

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