dual vs single carb - Snowmobile Forum: Your #1 Snowmobile Forum
User Tag List

 
LinkBack Thread Tools Display Modes
post #1 of 11 (permalink) Old 12-13-2012, 01:30 AM Thread Starter
-LIFETIME MEMBER-
 
Viktory2k1's Avatar
 
Join Date: Feb 2005
Location: Waukesha, Wisconsin
Posts: 335
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
dual vs single carb

I have seen many posts like this and still do not understand. I want to dual carb the '77 John Deere Cyclone 440 fc but ppl say that it wouldn't realy help on power. A liquifire has 58 hp and mine has 44, only dif is 2 carbs and liquid cooling? Is it a whole different motor? Bore and stroke same, comp ratio same.
I know there cast differently but same specs and 14 more hp?
Same drivetrain also.
Viktory2k1 is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 12-13-2012, 02:12 AM
Super Moderator
 
BC_Dan's Avatar
 
Join Date: Jan 2004
Location: oregon
Posts: 13,333
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 14 Post(s)
One big issue in making HP is getting rid of the heat. Liquid cooled engines are more effective doing that. If you can figure out how to get rid of the heat in the fan, then you could theoretically produce the same amount of HP with the same displacement/compression/carburation.

2007 Dragon RMK 700 155", 2008 RMK 600 155", 95 Prowler 550 2-up, Really OLD AC Cheetah

http://www.avalanche.org/accidents.php
BC_Dan is offline  
post #3 of 11 (permalink) Old 12-13-2012, 08:04 AM
Super Moderator
 
RJ Gleason's Avatar
 
Join Date: Feb 2005
Location: Groton NY
Posts: 33,201
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
You might gain a couple of ponies, but the biggest gain would be throttle response and the ability to jet each cylinder specifically to improve efficiency.

Since the PTO cylinder typically runs hotter, you could jet for that and run the other a size leaner as it runs cooler being next to the fan.

Old Cat Rider
'93 Wildcat 700EFI
w/ Comet 108 Pro-4 clutch & 01 ZR skid

http://www.dcdrifters.net/

Worshipful Master; F&AM Dryden Lodge# 472
http://www.masonicdryden472.org/

Rules of this forum are strictly enforced!
RJ Gleason is offline  
post #4 of 11 (permalink) Old 12-13-2012, 06:12 PM Thread Starter
-LIFETIME MEMBER-
 
Viktory2k1's Avatar
 
Join Date: Feb 2005
Location: Waukesha, Wisconsin
Posts: 335
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Would this change the rpm power band? Without looking in manual, my peak hp in the mid 6K range while the liquifires is in the mid 7K area. I dont know if mine would tolerate mid 7K or would it? Maybe the liquifires are balanced better. I dont know, this is still a pipe dream, lots to figure out I guess. Someone on here must to have tried this.
Thanks,
Vic
Viktory2k1 is offline  
post #5 of 11 (permalink) Old 12-14-2012, 09:14 AM
Super Moderator
 
RJ Gleason's Avatar
 
Join Date: Feb 2005
Location: Groton NY
Posts: 33,201
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
No, it would not change the power band significantly.
At the most, only a couple hundred rpm.

Old Cat Rider
'93 Wildcat 700EFI
w/ Comet 108 Pro-4 clutch & 01 ZR skid

http://www.dcdrifters.net/

Worshipful Master; F&AM Dryden Lodge# 472
http://www.masonicdryden472.org/

Rules of this forum are strictly enforced!
RJ Gleason is offline  
post #6 of 11 (permalink) Old 12-14-2012, 09:27 PM
I am Spartacus
 
smallengineguy's Avatar
 
Join Date: Feb 2004
Location: Milton Mills, NH
Posts: 23,793
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
The problem with adding 2 carbs is you also need to add more air and more room in the cylinder to put it all. That liquid engine was designed for 2 carbs, with a longer/bigger stroke. If you added another carb, you'd have to jet it super lean so it would not flood, to the point where you're pushing as much fuel as the one carb you had before.

1992 Ski Doo Mach 1 (SC-10/2 suspended) March '07 SF.com Sled of the Month! (Lost in fire 4-7-13)
1992 Ski Doo Mach 1 original
2006 Ski Doo MXZ 500SS
1999 Ski Doo MXZ600
Webmaster Evergreen Valley Snowmobile Club
SledNH.com Moderator
smallengineguy is offline  
post #7 of 11 (permalink) Old 12-15-2012, 12:14 AM Thread Starter
-LIFETIME MEMBER-
 
Viktory2k1's Avatar
 
Join Date: Feb 2005
Location: Waukesha, Wisconsin
Posts: 335
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
I thought bore and stroke were the same..
Not sure but going to abandon that project(dual carbs) I just thought someone on here did it and could post the results....
Viktory2k1 is offline  
post #8 of 11 (permalink) Old 12-15-2012, 09:58 AM
Registered User
 
WWTSE670's Avatar
 
Join Date: Feb 2012
Posts: 39
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I had a twin tilly set up on a old silver bullet. The thing was ridiculously finicky but the days that it would run right it absolutely ripped. Ended up going to a single carb in the end. The engine definitely generated more heat, and PTO side had to be jetted so fat that idle was almost compromised. It was fun though.


Sent from my iPhone using Snowmobile.com Free App
WWTSE670 is offline  
post #9 of 11 (permalink) Old 12-16-2012, 12:15 AM Thread Starter
-LIFETIME MEMBER-
 
Viktory2k1's Avatar
 
Join Date: Feb 2005
Location: Waukesha, Wisconsin
Posts: 335
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
I actually used to have a silver bullet. It was a 72 ski-doo 340 tnt. Not sure if its the same as what a real silverbullet is but everyone who saw said it was.
Not going to do it.
Viktory2k1 is offline  
post #10 of 11 (permalink) Old 12-16-2012, 01:09 AM
Registered User
 
WWTSE670's Avatar
 
Join Date: Feb 2012
Posts: 39
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Mine was a 294 I believe. Don't let me discourage you. Im sure if you took the time to dial in a couple of carbs you could get it to work right, I think my main issue was working with twin tillotsons. Mikunis seem more feasible


Sent from my iPhone using Snowmobile.com Free App
WWTSE670 is offline  
post #11 of 11 (permalink) Old 01-10-2013, 09:37 PM
Registered User
 
Join Date: Feb 2007
Posts: 621
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
You can't take what you know about 4 stroke engines like from cars and directly apply it to 2 strokes because they don't work the same.
The biggest problem with air cooling an engine is to balance cooling across the entire cylinder and head without having hot spots. Liquid cooling solves that problem handily. Since you don't have to worry about hot spots you can be much more aggressive with your porting, so more larger transfer ports which more effectively deliver the fuel/air charge from the bottom end into the cylinders, you can also run larger exhaust ports because you can keep them from burning away like they would on an air cooled machine.

So while the bore and stroke is the same its not like your engine is the same engine with just a cooling jacket wrapped around it.

Don't let that talk you out of dual carbs, many manufacturers did dual carbs on air cooled machines.

Raising sleds from the dead in north central MA.
'70 Ski-Doo Olympique 12/3 - The Yellow Bullet
'71 Arctic Cat Panther 303 - Wankle Panther
'78 Arctic Cat Pantera 5000 - Back from the dead!
'79 Polaris Cobra 340 - Back from the dead!
'95 Ski-Doo Grand Touring SE 670



www.deadsledwrenchers.net
curtludwig is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome