|
Post by theswede on May 28, 2009 8:10:26 GMT -5
I have an idea I wanted to bounce off the experts here:
I can easily get a 19mm carb for a cut-off saw (same carb as on a chainsaw basically), and am thinking of adapting it to fit on my scooter. Now, that carb is something like 1/4 of the size of the original carb, and can be mounted in any angle. It even contains a internal fuel pump... So my thought is that I'd make an adapter and mount it vertically right on the intake! Doing away with the intake pipe and getting a straight draft down thru the carb should increase the performance of the carb and of the engine, at least that is what I think. The intake filter will easily fit above the carb since the carb itself is so small... An added advantage is that these carbs come with completely adjustable low and high speed jets. I will be able to change jetting by using a simple screwdriver... :-)
Am I completely in the wrong here, or do you guys think this would work? Does the intake pipe have to be a certain length in order for the carb to work properly for instance?
/Otto
|
|
|
Post by Rebel on May 28, 2009 15:09:34 GMT -5
Sounds like something to play with, on a multiple cylinder motor I don't think it would be a good idea but on a single it might be great. I do know that distance is a factor in particle distribution and it might effect how well the air/fuel mixture ignites. But if the carb is cheap enough and if you want to play with it, hey sounds like a fun thing to try.
|
|
|
Post by theswede on May 28, 2009 16:25:19 GMT -5
Well, the carb is free so... :-) I'll just have to find the time to make the adapter.
|
|
|
Post by kliff on May 28, 2009 16:37:23 GMT -5
I think I'd run 1>1.5" manifolds. Just to be sure fuel dispersion is adequate. Don't be afraid to go longer, and play with differring tuning scenarios.
Over the years, I've seen home made maniflods with rubber tube center sections, of up to about 18" long...placing the carbs damn near into the startosphere above an ole dodge hemi... then I've see 8, yeah EIGHT, McCollough, M-101 diaphram (go-kart) carbs on homemade manifold adorning a small block chevy V-8....never did talk to the owner, so I don't know the displacememnt, but it was powerring a ski boat in the mid 60's.
Many jet skis use diaphram pumper carbs, been doing some shopping in that market recently myself...
|
|
|
Post by Enviromoto on May 28, 2009 16:48:28 GMT -5
You would definitely be the first. Not sure that on this small of a motor that it will make that much difference stock but if you port and polish the head, throw in a cam, and a big bore kit it couldnt hurt. It would also be harder for the carb to suck in air under the seat though.
|
|
|
Post by theswede on May 29, 2009 4:08:55 GMT -5
Kliff
I'll most likely have a mainfold/adapter of about 1" or a little longer, need to be able to bolt the thing to the head fairly easy :-) I'll also check the mainfold length used in the cut-off saws these things are intended for, it is most likely pretty short as these saws are extremly compact.
enviromoto I already have a 72cc and a performance cam on the engine. Can't remember if the valves are larger than stock though. I did replace the head, but it was some time ago. Port &polish will probably not be done at this time. I don't want to tear down the whole engine right now.
|
|
|
Post by kuzikood on May 29, 2009 10:36:21 GMT -5
um arent most chainsaws 2 strokes ? is the scoot a 2 stroke ? just thought id throw that ut there just to be sure
|
|
|
Post by Rocketdog on May 29, 2009 18:13:47 GMT -5
Sounds like a good idea that ought to be tried. Normally a long intake track benefits low end torque and a short one upper end horse power. Kliff I think it was the old Max Wedges 413-426 cid that had the long intake tracks that went to either side of the valve covers. I've seen old 392s with a variation of that. 1960 413 Wedge 1962 426 Wedge
|
|
|
Post by felliott on May 29, 2009 20:27:18 GMT -5
The brigges/stratton 4 stroke engine on racing go carts use a diaphragm style carburetor. they are bigger than the one you want to use, but if you go look at one you can see how they hook the pulse line up. Also you could ask them what RPMs they are running and the length of the intake runner.
|
|
|
Post by Rebel on May 29, 2009 23:01:58 GMT -5
felliot,
Welcome to the forum.
|
|
|
Post by kliff on May 30, 2009 17:23:17 GMT -5
Sounds like a good idea that ought to be tried. Normally a long intake track benefits low end torque and a short one upper end horse power. Kliff I think it was the old Max Wedges 413-426 cid that had the long intake tracks that went to either side of the valve covers. I've seen old 392s with a variation of that. 1960 413 Wedge 1962 426 Wedge Uhhhhmmmm, yeah, but back even before those, a group of young Dodge engineers form a club, called the Ramchargers, and even though this is a replication, it is pretty true to the original....rubber tube intakes to a plenum box, supprted by angle iron....and you thought tunnel rams were tall....passhhaw......
|
|
|
Post by felliott on May 30, 2009 18:39:30 GMT -5
Diphragm carbs use base pressure and vacuum to operate the the diaphragm. That is why you see them on two stroke engines. To put these carburetors on a four stroke you need a pulse hose. It connects to the 4 stroke intake runner very close to the block. If you look at the end of your carburetor by flange that bolts to the engine you will see a very small hole. This hole is the one works the diphragm. that is where you need to install one end of the pulse hose. the other end I all ready dicussed. The pulse hose doesn't care how long the intake runner is. That is why I told you to look at 4 stroke go carts. Being a long time drag racer with Dodge engine I can tell you as you tune your intake runner it will change the the power band to a narrower one. The picture of the old 413 wedge tourque was at around 3000 rpms. I worked for Dodge when they came out. they were great engine to have if you were pulling a trailer They were a bad engine for max performance.
|
|
|
Post by Rocketdog on May 30, 2009 20:09:14 GMT -5
LOL That's all true Kliff. Spawned the Red Ram Dodge 331, 354, 392. The first was in '51 I think. Desoto made one in '54. At one time Chrysler was the only US car maker to have it's own engineering school. Not the same subject, but my Grandfather was the Packard, Lincoln dealer in town. I've had
1966 Belvedere 426 hemi 4 speed <First year for the new Hemi> 1967 Coronet R/T 440 Magnum 727 auto <Was my Gandfathers car he left me> 1968 Roadrunner 383 Magnum 4 speed <Sold new for 1995.00. Hard to believe now.> 1969 GTS Dart 340 Magnum 4 Speed
All gone. Being young and stupid. Wrecked, blown up, or destroyed. I'd give all my toys to have that Coronet back. It meant something to me.
|
|
|
Post by Rocketdog on May 30, 2009 20:10:19 GMT -5
Sorry theswede. I stole the thread. My apologies.
|
|
|
Post by theswede on May 31, 2009 15:33:27 GMT -5
No problem rocketdog, that was some interesting trivia anyway.
Since I know the people who designed both the carb itself and the engine they are used for I'll make sure to involve them in this. I am certain they can provide some more hints.
kuzikood The engine the carb is built for is a 2stroke but the carb will work on a 4stroke, no problem.
|
|