jetting help on a built 450r

[mhewitt]

Ok so I finished getting my motor together n need some jetting advice, its a 450r with a 3mm stroker kit and a 3mm big bore. Should be around 497cc's I think. Using a crf 450 head with a hotcam stage 2, airbox lid off with uni filter, and hrc exhaust. Any ideas of what size jet kit to buy to get me in the right direction?

[robinson446]

start with 190 and go from there

[DnB_racing]

Originally posted by mhewitt
Ok so I finished getting my motor together n need some jetting advice, its a 450r with a 3mm stroker kit and a 3mm big bore. Should be around 497cc's I think. Using a crf 450 head with a hotcam stage 2, airbox lid off with uni filter, and hrc exhaust. Any ideas of what size jet kit to buy to get me in the right direction? im assuming your still using the stock carb,if so 190 is way too big

bore and stroke shouldnt have much affect on the air fuel mixture, and the head will have a little effect as the flow will be changed but the flow at that point is for both fuel and air so the jetting wont have a huge difference

the jetting difference wont be as much as changing the intake or exhaust, what comes in and what goes out has the biggest effect on the mixture..

with this being said depending on fuel and altitude and temp, I would give a guess of around 170 main and 48 pilot... but keep an eye on plug and listen to what the throttle position tells you

I would get this one it has the good needle and all the jets you should need http://cgi.ebay.com/ebaymotors/Keihin-FCR-Jet-Kit-TRX450R-TRX450ER-TRX-450R-450ER-450-/220775525958?pt=Motors_ATV_Parts_Accessories&hash=item33673f2e46 just make sure he send Keihin sometimes he uses AB instead of the keihin

[mhewitt]

I asked black sheep what jetting he runs n his trikes with the crf heads and he said with a crf carb he uses 178 main and 42 pilot so if bore n stroke doesn't make much difference then this should be close to what I need right?

[DnB_racing]

Originally posted by mhewitt
I asked black sheep what jetting he runs n his trikes with the crf heads and he said with a crf carb he uses 178 main and 42 pilot so if bore n stroke doesn't make much difference then this should be close to what I need right? I think the jetting on the crf carbs depending on the year carb he uses is a larger jet the the trx carb, if your using the+06 trx carb if you jet at 178 you might be a little to rich,

but jetting is one of those things ... you and I could be running exact same setup at he same place side by side, and our jetting would be slightly different,

at 178 at least you know you wont be lean, start there and try it, but im guessing that you will end up around 170-172 on the main and 45 or 48 pilot..

but if I was you I would still use the kit from xcbobs the link I gave you, and use the NCVQ needle(best needle),
just have him give you a couple sizes larger in the main and not the small ones, he will customize it for you,

I can just about guaranty you wont need the 160-162 mains,so have him give you a 178 and 180 instead, but I really think you wont need to go that big... im still sticking to my original guess of 170...let me know how close I am, and please let me know how the head performs

[mhewitt]

I'll be ordering the kit today n should be able to give you some info on what worked best in a week or so, thanks

[mhewitt]

the guy from that link wont let me substitute any of the jets for diff sizes, said i had to buy them individually. just to be as close as possible, im runnin 93 octane fuel, i live in eastern nc so pretty close to sea level, and the temp has been averaging 90F for a while now

[DnB_racing]

thats to bad, he used to be very good.

start on the rich side and work down to were it feels and sounds and runs the best,

if your still getting that kit, I would just to get the needle

,and start middle clip on needle and 175 on the main, and 48 on the pilot, and go down from there

[mhewitt]

Started with the 178 main 2nd clip fuel screw two turns out using hrc needle and acc pump settings and when I hit the throttle quickly it bogs. With the choke on it seems to handle the throttle better without bogging as much. Doesn't that mean it needs more fuel?

[mhewitt]

Also am using a 42 pilot would that be the one I need to go up in size on?

[DnB_racing]

im not saying the pilot and air circuit is were it belongs yet, but if its bogging with a quick stab, more then likely its the leak jet,or something with the accelerator pump

if you hold gas at around 1/8 open what happens, to adjust the jets just hold the throttle steady at 1/8 then 1/4 then 1/2, 3/4 then full, preferably going up a small upgrade, this way you put a load on the motor

[mhewitt]

is it ok to let it rev like that on the first tank of gas on a new motor or should i wait till im through my break in a little before worrying about the jetting? leak jet was either a 70 or 75 i believe, cant remember exactly. what is stock size? does that change with hrc jet kit? i turned acc pump out 1 and 1/8 turns like it says with hrc kit

[mhewitt]

Ok so when I give it throttle in 1/4 increments it does fine other than a lil popping when I let off from full throttle. But I hopped on it this morning n it ran like crap with it being 75 degrees outside. Yesterday afternoon when it was 99 degrees it ran way better almost perfect. So I put the air box lid back on this morning and then it ran a lot better, still would bog if u stab the throttle but was smooth otherwise. What should I try to change to fix this?

[DnB_racing]

i have a 55 leak jet in mine and its much better,bog is still there at times but,not nearly as bad

[mhewitt]

Dirtwheels mag just did a 450er build 06 model and they used the same big bore kit and the same cam as I am but they ended up with a 180 main. I think my 178 is a lil lean and their settings would suggest the same

[DnB_racing]

Originally posted by mhewitt
Dirtwheels mag just did a 450er build 06 model and they used the same big bore kit and the same cam as I am but they ended up with a 180 main. I think my 178 is a lil lean and their settings would suggest the same ok...

it seams huge to me, but you know how yours is running.

the biggest Ive seen on the frc carb for the 450 big bore ported has been 175, and that was with a FC intake and a sparks exhaust....

you just became officially the largest size main on any +06 450r ive heard about... lol

let me know where you end up and your mods, I guess those CRF heads have some serious increase in flow

[mhewitt]

Gonna go down a position or two on the needle to richen it up a lil bit n go up to a 48 slow jet and go down to a 55 leak jet n see how it does before going up on the main

[brewster426]

I run a 175 in mine. With the air box lid off and exhaust. I talked to Joe Byrd at a local track around here a few months ago and was asking him about jetting. He says on his practice bikes, air box lid off, hrc cam, and dasa full system he runs a 185. If I were you I would grab a 190 and see what happened. Maybe bigger.

[DnB_racing]

Originally posted by brewster426
I run a 175 in mine. With the air box lid off and exhaust. I talked to Joe Byrd at a local track around here a few months ago and was asking him about jetting. He says on his practice bikes, air box lid off, hrc cam, and dasa full system he runs a 185. If I were you I would grab a 190 and see what happened. Maybe bigger. come on really!!! are you sure he is using a +06 frc carb,

the 04/05 carb that's about the right size for a built motor,

but the +06 on any that ive tuned (around 10 of them)with almost evey different mod available except the crf head, the largest Ive ever used was 175 at 2000 feet and the 175 was in the winter and had to be jetted to a 172 in the summer, and that was with a web cam no air box and fuel custom intake and a full sparks exhaust, ported, high compression... you can try to go that big but I would be surprised if you dont hit a false rev limit from it 4 cycling

[brewster426]

The bike was a 08 I think..when I bought mine brand new I put the exhaust on. Took the air box lid off and put a 152 in it. It would be ok just revving it up but it would fall on it's face under load. Put a 160 something in it and it got better. Ended up with a 175 and runs like a champ. It had a 120 something in it from the factory. Huge jump I know. But it wouldn't even attempt to run right with a 150 jet. I live in the Memphis, tn area. I don't think it's anywhere near 2000 ft

[mhewitt]

I know im digging up on old thread but, the bike has been sitting for a while due to the expansion of my family so i decided to sell it to a friend. The main jet was up to a 200 and i cleaned the carb got it running good again but at 3/4 to full throttle it still feels like its running out of fuel. Feels like the petcock is off and running out of gas. Best way i know to describe the feeling. We put a 210 in it same result maybe SLIGHTLY better. He ordered a 220 but hasnt installed yet. Runs good everywhere but 3/4-full throttle, other than popping on decel. Bike is extremely powerful but falls off top end and feels like its running out of gas. I suggested he take it to a tuning shop to dyno tune but nearest is four hours away. Any insight?