Carburetor upgrade questions alky - Yamaha Raptor Forum
 
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post #1 of 9 (permalink) Old 07-10-2019, 01:33 PM Thread Starter
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Carburetor upgrade questions alky

I am looking to upgrade my stock carbs to a single or a dual on alky

some of the carbs I have thought of were a 44 mikuni super bn a 45 mm tillotson (very unlikely as those cost a arm and a leg) a set of 35 mm pwk airstriker replicas or a mikuni hsr 45 i am willing to build a manifold

do any of you have any ideas of other carbs or jet sizes from what i read i probably need 230-260 cfm id pefer a single carb because they are easier to tune but it may not get enough fuel

this is going on a go kart the frame I have worked and shortened the wiring harness (everything surprisingly worked out) the carbs that were on it are junk (terrible condition)

14:1 comp, was on 110 the head is mildly ported cfm unknown most likley 230-260 cfm, stage 3 hotcam, stronger valvesprings, 102 mm bore with a 4 mm stroker around 720cc the guy i bought it from said it had 85-93hp.

ran great (when not having carb issues) to give you a idea when it was on the atv would pull wheelies in 4th with the slightest bit of clutch and powerwheelie in 3rd on stock size gears

i am new to this motor bought it off a guy with a blown out transmission a few years back and fixed that pulled it off the atv due to a charging system malfunction could not get it working so now it is going on a go kart with a small 12v battery to replace the charging system that will be recharged every race the starter will be externally powered. it does function and run for up to 3 hours then the battery dies

I am getting rid of the stock carbs because 1: i don't like the design 2:never could get enough fuel 3:constantly broke and it has a crack somehow on the large side

running up against snowmobile motors and 450s bored out to 500 on alky

2004 660r engine on a 2015 millennium racing chassis fa**** wedge (prototype stage) big bore, stroker a whole butt-load of headwork stage 3 cams theres a whole lot more thats just the big stuff looking for a coil 90+hp
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post #2 of 9 (permalink) Old 07-10-2019, 01:36 PM Thread Starter
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I will most likely delete the radiator if I can get it running cool enough

2004 660r engine on a 2015 millennium racing chassis fa**** wedge (prototype stage) big bore, stroker a whole butt-load of headwork stage 3 cams theres a whole lot more thats just the big stuff looking for a coil 90+hp
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post #3 of 9 (permalink) Old 07-10-2019, 06:24 PM
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Either the head is much more than “mildly ported” or the horsepower estimate is way off.

I would think, from what I know dealing with 700s, youde want around a 54mm carb for an alcohol based fuel at that power level.

2015 700Rse
Fci, PC5F/I, monster exhaust, +2 Cuervo head, HDD5150, 54mm throttle body, 105.5 14:1, +8 swingarm.
08 yfz450se
Sparks big core, k&n no lid, yz needle, yz timing mod, +4 swingarm.
“Peepshow”
Cuervo 870, lectron, msd, monster megs, single a-arm lightened chasis, +14 swingarm.
”Monarchy”
Cuervo 930, lectron, msd, db fab titanium chasis.
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post #4 of 9 (permalink) Old 07-10-2019, 07:31 PM Thread Starter
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Quote:
Originally Posted by t web2007 View Post
Either the head is much more than “mildly ported” or the horsepower estimate is way off.

I would think, from what I know dealing with 700s, youde want around a 54mm carb for an alcohol based fuel at that power level.
thats what i assumed it was around the guy who sold it to me never told me the numbers thats my guess he just told me hp and bore stroke compression cams etc and his dynos hp he said it makes in its powerband 85-93 hp depending on conditions

i have 55 gal of alky for my other motors so i would rather have it on alky then 110 because alky is more accessible

there are no 54 mm carbs the biggest i have ever seen as a single is a pwk48 but i think that would be pushing it the guy i bought it from had a diffrent carb he took off it and gave me this piece of junk i think its a stock replica he said it was meant for 110 and it always ran like crap and i found out there was a crack on the casting so im looking for something else

2004 660r engine on a 2015 millennium racing chassis fa**** wedge (prototype stage) big bore, stroker a whole butt-load of headwork stage 3 cams theres a whole lot more thats just the big stuff looking for a coil 90+hp
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post #5 of 9 (permalink) Old 07-10-2019, 10:23 PM
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Quote:
Originally Posted by williamrheawe View Post
thats what i assumed it was around the guy who sold it to me never told me the numbers thats my guess he just told me hp and bore stroke compression cams etc and his dynos hp he said it makes in its powerband 85-93 hp depending on conditions

i have 55 gal of alky for my other motors so i would rather have it on alky then 110 because alky is more accessible

there are no 54 mm carbs the biggest i have ever seen as a single is a pwk48 but i think that would be pushing it the guy i bought it from had a diffrent carb he took off it and gave me this piece of junk i think its a stock replica he said it was meant for 110 and it always ran like crap and i found out there was a crack on the casting so im looking for something else
Lectron makes big carbs, I have a few, up to 58mm in their standard body.
The common bigger carbs on 660s are dual 39mm fcrs.

Have you thought about starting with a good set of oem carbs and going from there?

2015 700Rse
Fci, PC5F/I, monster exhaust, +2 Cuervo head, HDD5150, 54mm throttle body, 105.5 14:1, +8 swingarm.
08 yfz450se
Sparks big core, k&n no lid, yz needle, yz timing mod, +4 swingarm.
“Peepshow”
Cuervo 870, lectron, msd, monster megs, single a-arm lightened chasis, +14 swingarm.
”Monarchy”
Cuervo 930, lectron, msd, db fab titanium chasis.
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post #6 of 9 (permalink) Old 07-11-2019, 02:20 AM Thread Starter
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Quote:
Originally Posted by t web2007 View Post
Lectron makes big carbs, I have a few, up to 58mm in their standard body.
The common bigger carbs on 660s are dual 39mm fcrs.

Have you thought about starting with a good set of oem carbs and going from there?
oem carbs dont flow enough fuel for methanol and lectron carbs are way out of budget as they are almost twice the price of a tillotson which was high priced in the first place at this point

from further reading i think i will end up running a set of PWK 38mm flatslide carbs while building a intake out of aluminum 6061 tubing 40 mm od 36mm id 300 mm long tube which i will cut and level to length and port out to 37.5 to 38 mm and a moose racing intake spacer that i will port match and use as a flange and fit the tubing to size i would weld them together and fit the tubing to the port

so next i will have to figure out jetting 170 Main Jet 55 Pilot Jet is factory obviously too rich for gas so will be setup for alky as planned so figuring the 230% increase rule and the recommended jetting from most posts as a base the main jet will need to be a 340 and the pilots 90-100 i will have to make these this size due to those not existing which means drilling and i have found the drill bits needed i am sure this is correct do you see any problems i would rather not go with a 39 because i wouldn't be able to find the right tubing to make the intake

2004 660r engine on a 2015 millennium racing chassis fa**** wedge (prototype stage) big bore, stroker a whole butt-load of headwork stage 3 cams theres a whole lot more thats just the big stuff looking for a coil 90+hp

Last edited by williamrheawe; 07-11-2019 at 02:24 AM.
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post #7 of 9 (permalink) Old 07-11-2019, 07:32 PM
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Quote:
Originally Posted by williamrheawe View Post
oem carbs dont flow enough fuel for methanol and lectron carbs are way out of budget as they are almost twice the price of a tillotson which was high priced in the first place at this point

from further reading i think i will end up running a set of PWK 38mm flatslide carbs while building a intake out of aluminum 6061 tubing 40 mm od 36mm id 300 mm long tube which i will cut and level to length and port out to 37.5 to 38 mm and a moose racing intake spacer that i will port match and use as a flange and fit the tubing to size i would weld them together and fit the tubing to the port

so next i will have to figure out jetting 170 Main Jet 55 Pilot Jet is factory obviously too rich for gas so will be setup for alky as planned so figuring the 230% increase rule and the recommended jetting from most posts as a base the main jet will need to be a 340 and the pilots 90-100 i will have to make these this size due to those not existing which means drilling and i have found the drill bits needed i am sure this is correct do you see any problems i would rather not go with a 39 because i wouldn't be able to find the right tubing to make the intake
Not sure on the physical size of those carb bodies, but a manifold already exists for kehin 39 fcr kit for raptor 660.

I suggested trying good oem carbs because you said in the first post that the bike ran great when not having carb issues, on 110 and that the carbs were Oem replicas. You also said the bike makes somewhere around 90hp with a “mildly ported head”. Some of that information is absolutely false, you need to figure out which part, or you’re just chasing your tail.

2015 700Rse
Fci, PC5F/I, monster exhaust, +2 Cuervo head, HDD5150, 54mm throttle body, 105.5 14:1, +8 swingarm.
08 yfz450se
Sparks big core, k&n no lid, yz needle, yz timing mod, +4 swingarm.
“Peepshow”
Cuervo 870, lectron, msd, monster megs, single a-arm lightened chasis, +14 swingarm.
”Monarchy”
Cuervo 930, lectron, msd, db fab titanium chasis.

Last edited by t web2007; 07-11-2019 at 07:36 PM.
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post #8 of 9 (permalink) Old 07-11-2019, 10:39 PM Thread Starter
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Quote:
Originally Posted by t web2007 View Post
Not sure on the physical size of those carb bodies, but a manifold already exists for kehin 39 fcr kit for raptor 660.

I suggested trying good oem carbs because you said in the first post that the bike ran great when not having carb issues, on 110 and that the carbs were Oem replicas. You also said the bike makes somewhere around 90hp with a “mildly ported head”. Some of that information is absolutely false, you need to figure out which part, or you’re just chasing your tail.
what is the stock port vs modified look like i have no clue this is the first ohc engine i worked with i normally work with ohv and flat head motors gx390, gx200 g200 briggs 5 hp briggs blockzilla clone hondas etc

i know the carbs were modified because i see that they have reemed out substantially they were either 35 or 36 mm on the high side and 34-35 on the low side my calipers need re-calibrated they are a little off sometimes they will subtract a mm

i have never worked with these heads before i had the cam out to make sure it was a stage 3 hotcam as i had my doubts i know was true exhaust was around 10.81 to 10.82 mm intake was 10.14-10.15 they seem worn .01-.02 mm i used a dial indicator to check this and duration checked out fine i checked the bore and compression it ran fine but never did it do great at the high end above 6500 rpm and above 8000 it felt like it didnt have enough fuel

but the main problem with fcrs is to set a set up for alcohol that will cost you nearly 800-900 dollars i can setup a set of pwks for 300-350 dollars and it really inst that hard to build a manifold as i have done it before

Last edited by williamrheawe; 07-11-2019 at 11:14 PM.
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post #9 of 9 (permalink) Old 08-05-2019, 10:03 PM Thread Starter
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she still is a little lean and the smoke is oil on the exhaust it sounds better in person on camera it comes a little raspy

2004 660r engine on a 2015 millennium racing chassis fa**** wedge (prototype stage) big bore, stroker a whole butt-load of headwork stage 3 cams theres a whole lot more thats just the big stuff looking for a coil 90+hp

Last edited by williamrheawe; 08-05-2019 at 10:05 PM.
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