Yerf Dog back fire at idlel only

[BEEFKING69]

Picked up excellent condition Spiderbox that just needed carb cleaned but it idles up and down and backfires every noe an then but only while idling. runs good till top speed then feels like its bucking just a lil bit. have also tried new carb and still does it but not as bad.

[liduno]

Kinda sounds like a vacuum leak, maybe the rubber intake is cracked?

[BEEFKING69]

intake is also new....havent replaced spacer or gasket under the spacer tho

[xlint89]

Backfire through carb or exhaust?

[BEEFKING69]

carb...ive replaced the spacer gasket but something still dont seem right and now its backfiring in exhaust on deceleration.....that could be exhaust gasket tho. valves have been set btw

[tkeagle]

Does sound like vacuum leak. But I've had problems before, when I first got the YD, that the wire connections on the coil was not getting good connection. And was acting the same way. Really noticed it when you gave it more throttle.

Also, I half to keep an eye on the clamps from the carb. to the rubber intake. If not placed correctly, the bottom of carb. will slide off a little and cause a vacuum leak. But has happened enough times, I know right away when it does do that.

[xlint89]

I agree with TK, I had a coil issue that would simulate a carb problem at WOT. It would spit and sputter. A quick coil change (also inspect wire connections) can eliminate that from the equation.

You also noted a NEW carb? Did you install the original jets from the OEM carb into it? Those cheapy replacement carbs come with odd sized jets sometimes.

If you suspect a vacuum leak, spray around all mating surfaces of the intake/carb with starting fluid while running and see if you notice any RPM changes. That may help you identify a vacuum leak.

[BEEFKING69]

the connections at the coil was a lil loose so i tightened them and no on the carb i used legit jets but i have noticed all the new carbs ive bought have a 22mm slide where the stock carbs have 24mm slide and also ive found that theres atleast 3 different length pilot jets???

[SYCARMS]

The buggy carbs are 26mm as where the scooter carbs are 24mm. This is what is important on a CV carb which I assume you have. Slides can be of different sizes and won't really affect the performance. the carb size however will. Many new buggies have gone to the 24 mm carbs due to EPA emission standards. Your Yerf Dog should be a 26mm carb.. As far as pilot jets go there are long and short jets for the CV carb.. Some will come with the short pilot, I have used the long pilot with no problem.

[BEEFKING69]

where are you getting 26 from? at the butterfly side? so far all mine have measured 24 but id love to get some 26's

[SYCARMS]

Intake side ID.

[BEEFKING69]

all the ones i have... stock and new are 24 id intake

[SYCARMS]

That's the problem I have had lately. I used to get the Keihn or DENI carbs and they were 26 mm. That distributor is now defunct so I am looking for another source. Not long ago carbs were labeled either GY6 which were scooter 24mm and GY6 buggy which were 26 mm. All the new buggies now use the 24 mm carb I guess due to EPA since they run so lean. I am trying to find the 26 mm carbs but so far no luck. Don't know if they do not make them any more due to lack of demand. If I do find them I plan to stock several.

[GX150]

All the Yerf-Dog, Tomberlin and Baja GY6's I have seen used 24mm CV's. I'm pretty sure that Hammerheads and Carters also came with 24mm. I know the 250's came with 28mm or 30mm depending on the source. Are you sure about 26mm in the 150's? 26mm and 28mm were usually upgrades on the 150's.

[BEEFKING69]

Originally Posted by SYCARMS

That's the problem I have had lately. I used to get the Keihn or DENI carbs and they were 26 mm. That distributor is now defunct so I am looking for another source. Not long ago carbs were labeled either GY6 which were scooter 24mm and GY6 buggy which were 26 mm. All the new buggies now use the 24 mm carb I guess due to EPA since they run so lean. I am trying to find the 26 mm carbs but so far no luck. Don't know if they do not make them any more due to lack of demand. If I do find them I plan to stock several.

Do you have one you would sell? Id like to try one on my crossfire.

[SYCARMS]

Back in 2004 and into 2005 Carter in their 125cc used the 24mm, 2005 up to I believe 2007 Carter used the 26mm. My pre China built yerf dog when they were formed, welded and assembled in Mississippi has the 26mm. The Yerf Dog 150 UTV's I believed they were called scout used the Mikuni 26mm. Both my Blades come with 26mm. Kinroad used the 26mm as I believe so did Hammerhead.When MRP was still in business the carbs were listed for either GY6 or GY6 buggies. The only difference between the 2 were one listed for GY6 were 24mm for scooters the 26mm were for the buggies. In 2007 EPA started regulating the Chinese off road vehicles. Scooters had no problem passing EPA where as the buggies started down sizing the main jets. Buggies originally come with 118 main jets but in 2007 they dropped to 114 than 112 mains.In 2008 everyone had problems getting the buggies through EPA certification. That is when Carter went to SYM for their engines which basically looked the same as the regular GY6 but with redesigned valve angle and combustion chamber basically a revamped series B design. Kinroad was still sneaking them in using altered paperwork which later got them caught and their license was pulled by the EPA sometime in 2009. Hammerhead passed with their new design which incorporated the internal reverse which is currently used today. The first regulation EPA passed in 2007 was that all A/F adjustments had to be plugged and the breather hose had to run to the air box. I know this cause I had 25 carbs from Blade I had to modify than at the warehouse I had to swap them out on the crated buggies to make them compliant. All the carbs were 26mm. So yes I am absolutely sure. The performance carbs sold were either 30mm or 32mm. The 250cc buggies always had 29mm carbs on them. All the new style engines with the internal reverse HH, TM, ASW, Kandi all use the 24mm now in order to pass the EPA and also use smaller exhaust valves.
To answer BEEFKING69 no I do not I am trying to find them. All I have in 26mm is the Mikuni which went on the Yerf Dog scout. It is different in that it uses a manual choke and the bowl is deeper to where the intake would have to be spaced about 1" for it to clear. On the older buggies the 24mm will work but slightly undersized for the buggy especially with cam or head mods. The 26mm if perfect whereas the 30mm is too much carb unless one has extensive mods.

[GX150]

Both my 3206 and 4209 Yerf models were 2004's. Both came with 24mm CV carburetors with sealed air/fuel mixture screws and 110 main jets. Both were 100% stock when I bought them with no modifications. Yerf-Dog went out of business late 2005 or early 2006 before the EPA timeline you posted.

My 2006 Tank GY6 scooter used the same 24mm carburetor with sealed A/F screw and a 108 main jet.

Wasn't 2007 the introduction of tamper resistant float bowl screws so you could not easily alter jetting?

[SYCARMS]

Are you from California?

[GX150]

No, but one Yerf came from Sam's Club and the other from Pep Boys, so they could have come out of CA warehouses.

[GX150]

If you want go back into the old Yerfer.net archives to verify carburetor size, Buggy Depot has them online. Once you get to the Buggy Depot home page, add this to the end of it: http://www.**********.com/archives/yerfer.net/forums/

I cannot link the the page directly due to word filtering on this site.

[BEEFKING69]

Are you using the mikuni? If not what would you take for it?