Gearing and Jetting Suggestions for ESR 310 Kit

[YFZRob]

Hey everyone. I've got my ESR 310 bolt-on kit broken in now, and I'm ready for some WOT blasts to check jetting. I've got a 38 A/S, TRX-5 pipe, TRX-7 ported 310 kit, CR reed block, and pump gas dome in an ESR head.

First off...gearing. The previous owner put a 12 tooth front sprocket on it, and I have since purchased new renthal stock-sized 13/38 sprockets and a new stock length DID ATV X-ring chain. I am running 20" tires, and plan to stay that way. What would you all suggest for gearing for just a trail bike? Should I get a 14 tooth front instead of the 13? I notice a lot of you guys who run 18s have 14/38, which I would think would be similar to 13/38 on 20s.

Jetting. I have a 185 main, 50 pilot, and needle on 4th clip. I haven't gotten into the main yet, and it seems to be okay down low and up to 1/2 throttle. Being at sea level with my motor, would you suggest more or less on the main jet as a starting point?

Thanks!!

[zedicus00]

14 front prolly wouldnt hurt with 20's on a 330. i run 13/39 on 18" with a 246cc engine an like it.

[YFZRob]

I just finished installing the renthal 13/38 combo. I'm taking it out tomorrow to see how it rides. How many teeth can you go down on the rear before you run out of adjustment with the stock length chain? I was going to buy a 37 rear, but RMATV was backordered on them. Also, does anyone know what the calculation for teeth in the rear to teeth in the front? Meaning, does 3 rear teeth equal the same gearing change as 1 tooth up front?

[wilkin250r]

I'm not positive, but I think you're right, the stock gearing is 13/38.

That 310 will have a LOT more power than stock, you'll probably find the 13/38 inadequate. I'd try a 14t front, you should have the power to pull it.

The "change" for teeth in the rear compared to the front really depends on the specific gearing. The basic thing to do would be divide the rear teeth by the front teeth. For stock, 38 divided by 13 is 2.92, pretty close to 3. So one tooth in the front is about the same as three teeth in the rear. But if you're looking at a 400EX, say with 16/36 gearing (taller than stock), then one tooth in the front is only about 2 teeth in the rear, because 36 divided by 16 is only 2.25.

[beerock]

14/38 should be the ticket with 20's

your jettign sounds about right but you may need a 52 pilot?

unless esr reccomended the 50 pilot?

[YFZRob]

Yeah, ESR sent the carb with the 50 pilot and the needle setting on the A/S. They also sent it with a 190 main, but admitted to it most likely being overly rich.

I'll get the 14 front on order, but for the meantime, I'll enjoy the 13 on there now.....still a BIG improvement over the 12 tooth that the previous owner slapped on there.

On another note, I don't know if I can buy the Ohtsu's......unless someone can vouch that they'll hook well compared to Holeshot XCRs or HDs....or any other tires. I really dig the stock look....I just now realize how badly this thing needs traction!

[beerock]

Originally posted by YFZRob
Yeah, ESR sent the carb with the 50 pilot and the needle setting on the A/S. They also sent it with a 190 main, but admitted to it most likely being overly rich.

I'll get the 14 front on order, but for the meantime, I'll enjoy the 13 on there now.....still a BIG improvement over the 12 tooth that the previous owner slapped on there.

On another note, I don't know if I can buy the Ohtsu's......unless someone can vouch that they'll hook well compared to Holeshot XCRs or HDs....or any other tires. I really dig the stock look....I just now realize how badly this thing needs traction!


bro I used them in a sand race in wildwood nj and i holeshotted 3rd, with 6 banshees 1 lt250r and 4 other R's

[rs169300]

I think 14/38 is to high. I know when the top pros in GNCC were on 250r's they used a 13/37 combo. Most of them had more power too.

[wilkin250r]

Originally posted by rs169300
I think 14/38 is to high. I know when the top pros in GNCC were on 250r's they used a 13/37 combo. Most of them had more power too.

That's GNCC, pretty tight and technical, and running a 265cc, most likely ported and piped for low-end and midrange. If you're doing casual riding on a 310cc, you want to let it run out a bit...

[beak7707]

I bought a carb off of ESR and they had it pre jetted and it was spot on. I would think if they jetted it you will be real close.

[beerock]

Originally posted by wilkin250r
That's GNCC, pretty tight and technical, and running a 265cc, most likely ported and piped for low-end and midrange. If you're doing casual riding on a 310cc, you want to let it run out a bit...

i thought that was gnc? i thought gncc was any limit? balance ran a lrd 350p/v with the R, my bud had his old motor a while back.

[papatrx]

Jetting:
You must do your own jetting with your own plug chops! Your elevation, temperature, humidy and air density make your requirements different along with how your engine is set up. You need to take the time, start fat on the main and work your way down to where you get the proper color on the insulator from a chop. I have 6 of these bikes with the same pipes all within 2 bore sizes of each other with the same carbs and just minor differences in porting. They all run on the same hills in the same temperature at the same time and I have the main's ranging from 168 to 190.

I have a good bud that mx's professionally and he and 4 others with new 05 crf450r's with no mods, all have them jetted differently just for their own riding style.

It absolutely drives me nutts when people tell somone across the country what mains or clip position they should be using, it's not going to be accurate, when ESR pre jets a carb, its an estimate only and the fine tuning must be done by you.

Trust me, with all the bikes in our family, I sometimes feel like I spend more time jetting than riding, but a well jetted bike can make a huge increase in power all throughout the power curve, spend the time and learn to do it correctly and you will be faster on bottom and top.

[YFZRob]

I'm not looking for specific jetting recommendations, just suggestions from previous experiences as a starting point.

Doesn't matter much now, I did some WOT plug chops yesterday and was very pleased with the plug color....not black or wet, but a pretty healthy medium to dark brown.....I'm assuming a nice safe setting. This was with the 185 main.

This was the first time I have riden it at WOT, and the first time I've ridden it off-road. I'm pleased with the power, but due to massive tire spin, there's barely any noticeable difference between 60% throttle and WOT. The bike barely goes anywhere in 1st and 2nd, and slowly starts to scream in 3rd+ gears. Even in dry grass, it's a spin monster. I had quite a bit of roost in GRASS in 4th gear! I think I like the 13/38 gearing, even though it spins so badly in 1st and 2nd. The bottom end is gone that I had stock, which I was expecting, even with the TRX7 porting, so I think the 13/38 may work out better at lower speeds to keep it in the powerband in 2nd and 3rd gear. Sprockets are so cheap though, I'll grab a 14 tooth still to try it out. Thanks again for everyones help.

[papatrx]

A good safe color is cream coffee color, that will not be color for optimal power but good for engine safety and logevity. Since I recall you said you will be doing mostly recreational riding on this bike, don't forget to also do plug chops mid throttle for your clip setting, this can be just as important as the main especially for rec riding.

I have seen many mid throttle lean seizures.

[YFZRob]

papatrx,

That's the best way to describe the plug color...cremed coffee. It is a little too healthy, but like you said, it's safe. I may go down one jet size, but probably leave it alone.

Thanks for the suggestion on part throttle chops. I will definitely keep an eye on that too.

[zedicus00]

86 87 hav 13-39 88 89 hav 13-38 or am i backwards? but yes there is a 1 tooth change over the years. and actually jus ride it an gear it how it feals best to u.

[YFZRob]

You are correct. They went down to a 38 on the 88/89.

So far, it feels decent with the 13/38 spread w/ 20" tires. I think it will blow the tires off with virtually any gearing I put on it. :devil: Anyone have any idea if I'll run out of RPM in 6th gear with a 13/38? Or would it be drag limited? Assuming with my modifications. How fast should this thing be? Seeing how it pulls in 4th and 5th now, I'll be shocked if it cannot match my YFZ's 75 mph GPS recording.

[zedicus00]

maybe try a 13-36 or a 14-40? my lil 246R will do 70mph in a hurry. i bet yurs pulls harder but i bet u go thru gears way faast.

[YFZRob]

Yeah, it goes through gears as fast as it did stock with the 12 tooth front that the previous owner put on it. I LOVE shifting, but it's a lot of shifting to keep it in th meat of the powerband. I may try a 36 rear sprocket to be just a tad under a 14/38. Then again, the front sprocket is about 1/4 the cost of the rear, so maybe I'll give 14/38 a shot first.

[zedicus00]

yeah gearing is always a pain, i had a 12 on the front of mine for a while, its an 86 style trany so it made 6th usable in the sand but ended up makeing 1st useless. what yr of tranny is yurs? the 88 89 style is a lot more forgiving if yur sprockets arent exactly perfect for the engine. im running 13 39 with 18 inch tires on a wild 246 and it actually can pull in 6th gear but i would still rather hav a short rod engine with the 88 89 tranny.

[YFZRob]

Yeah, I have an 88 tranny. I'm not free to get out to Ocala National Forrest and really open her up on fire roads until the 27th. I think I'm going to go insane waiting for that day to come. Got shafted with my mother-in-law and my mom coming up this weekend....something my wife planned without my approval :mad:. Next weekend is out of town plans. :ermm:

[wilkin250r]

Originally posted by beerock
i thought that was gnc? i thought gncc was any limit? balance ran a lrd 350p/v with the R, my bud had his old motor a while back.

That's very possible. Here on the west coast, I don't pay too much attention to the particulars of east-coast and mid-west racing.

[beerock]

Originally posted by YFZRob
Yeah, I have an 88 tranny. I'm not free to get out to Ocala National Forrest and really open her up on fire roads until the 27th. I think I'm going to go insane waiting for that day to come. Got shafted with my mother-in-law and my mom coming up this weekend....something my wife planned without my approval :mad:. Next weekend is out of town plans. :ermm:

bro you have a 310, go with 14/38 or 14/37
also, put your weight on the rear seat and it will hook up n 1st AND 2nd, trust me. When i race i Start in second im all the way up on the tank watching the gate, i keep the throttle at half when the 10 second card is up i count back, after 5 seconds i hold it to 3.4 throttle watch the pin and hold it wot drop the clutch and push all my weight back on to the grab bar of the bike and hold on, shift it WOT to third. 4th etc.... if the front end comes up i feather the clutch to put it back down

seriously though, get rid of the 13 tooth and go with a 14 front.

if not go with a 13 36 which is almost like 14/39,

[YFZRob]

Okay, 14 tooth on order. We'll get 'er on there before next time out.