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Big Bore jetting

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So I've got a 05 chassis, with a 06 bottom end. A 05 head, and a 05 carb. 

Engine has been redone from top to bottom. New bearings, seals, crank, cylinder works 269cc big bore kit. Valve seats were cut, exhaust valves ground, and new oem intake valves & springs ect.

I'm running a stock exhaust, with after market air filter. 

I have a dyno jet stage 1 jet kit. 

Stock jetting for 05 is #172 main, #42 pilot, jet needle ncyq, clip position 3rd from top, and pilot screw 1 3/4 turns out. 

I was going to swap the needle to the dynojet, 3rd clip position, and change to a #45 pilot jet. 

What # main should I run? How many turns out on the Pilot screw?

For a base for me to start? My elevation is 850ft above sea level

The current jetting is stock, including the ncyq needle and clip position. Only thing different is a #45 pilot jet.

What do you suggest?

 

 

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When running a big bore you will need to lean it up somewhat due to the larger pluse it creates. I have run a number of big bores on crf 250s and always ended 1 leaner on the pilot and 2 on the main. So as a starting point run a 40 pilot and a 170 main leave to needle where it is and see.

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If you use the kit it will have instructions for sea level, 3-6k, 6-9K etc.  at 850' use the 3-6K instruction for a start.

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 NCVS needle 42 pilot 165 main jet and throw that dynoshitcrap in the trash, if your bike ran reasonably well before the big bore kit it should be reasonably close now but a little rich in comparison to the stock bore set up.

fuel screw starting spot should be 1 1/2 turns out run the bike untill warmed up good and tune the screw for best idle note that less than 1/2 turn out from lightly seated means you need a smaller pilot jet and more than 2 1/2 turns out try a bigger pilot jet. 

go look in the jetting n carbs area this has all been done many times before.

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3 hours ago, AlotL1keVegas said:

Isn't a NCVS needle for a 450r? 

My current needle is a NCYQ. 

yes among other bikes on the ncvs,  i find the ncvs works very well in a lot of bikes besides the 450, try it out i have a bunch of CRF250R and other bikes running on that needle and they all like it

read up on krannie,s posts about that needle

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Peaceofwork, got my new needle and jets today. Unfortunately I wasnt able to start it up yet due to a leaking stator cover. Soon as i do, I'll let you know the results.

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Got bike all together. Went to kick it over and it wouldn't start. All i got were 3 back fires from the exhaust. Ikicked it over for a solid 20 minutes. I pulled the spark plug, (it has spark), and there was a faint smell of gas. The plug wasn't soaked like I thought it would be after all that kicking. 

Almost seems like it's not getting gas? I didn't try starter fluid, fearing I'd burn up my brand new head I just had done.

#165 main jet, #42 pilot, NCVS needle at 3rd clip. Fuel screw 1.5 turns out. 

Pretty positive the timing is on. Although I haven't checked it yet. 

Any other ideas?

I have heard a couple horror stories of when someone blew up there bike, and the engine locks up, it twisted the cam chain gear on the cam shaft. So it will look like it's timed correctly to the naked eye, but in all reality, the cam isn't 100% true. Im thinking this is a worst case scenario, considering the old bottom end grenaded. I got a new bottom end, but I'm still using the original head and cam. 

What do you think?

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see if turning the fuel screw out helps ? 

sometimes these bikes are a bitch to start the first time after being apart, if it were me working on it i would confirm the timing marks are all good and recheck valve clearances then turn the fuel on and wait a min then lean the bike over until fuel gushes out the over flow hoses. stand the pike straight up fully open and close the throttle twice choke it and kick it like you mean it. 

to me a few things come to mind when you say 3 backfires

#bad timing

#bad old fuel

#perhaps your flicking the throttle when your kicking it as many 2 stroke guys do?- try getting your hand on the bar not the throttle when your kicking it. opening the throttle any amount as your kicking a 4 stroke leads to back fire.

if it still has not fired put the choke in and hold down the hot start and give it a half dozen kicks - if it starts that way consider that its rich fore some reason?  like maybe the float neads to be adjusted or has a hole in it? or elevation or temps?

my shop has a hill out front so my first start after a build is a bump start, its just so easy.

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Intake valves are .005 and the exhaust are .003. A little tighter then I'd like, but still technically fall in spec.

My timing marks on the cam sit level with head, and the right side marks line up perfect. But the marks on the flywheel don't line up with the left side case. 

I see 2 hash marks on the outer lip of the stator. And then towards the back of the stator, there's 2 other hash marks that are lines T & F. The manual says line T lines up with left case? Mine isn't even close. 

Am I missing something here? The flywheel is set with the key way. So it only goes on one way. Same goes for the gears on the counter balancer ect. They're all slotted. So they can only go on one way. It's practically dummy proof. 

When ones doing a compression test, should I zip tie the decompressor so it's not engaged to get an accurate reading?

 

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i think intake specs are 004- 006 you should be good their now exhausts at 003 seems a way to tight to me. confirm it but i,m thinking 010/012 is exhaust clearance or 009/011 ?

On 5/31/2017 at 6:52 AM, AlotL1keVegas said:

 

My timing marks on the cam sit level with head, and the right side marks line up perfect. But the marks on the flywheel don't line up with the left side case. 

I see 2 hash marks on the outer lip of the stator. And then towards the back of the stator, there's 2 other hash marks that are lines T & F. The manual says line T lines up with left case? Mine isn't even close. 

 

 

the best way i can explain this timing procedure to you is, you have 2 critical marks on your rotor .

only ever rotate your rotor aunticlockweise looking from the left side of the bike.

pull the spark plug to help with easily rotating the motor to find marks, as you turn the motor the first mark warnes you the second mark is about 3/8" away - the right side of the motor has a plug you can pull and then get an allen wrench in their to get a more controled movement of the motor. 

if all marks are not right remove the tensioner take off the cam caps slide the gear side bearing over closer to the gear tilt the cam up and while keeping the timing chain tight up to the crank gear rotate the cam which ever way it needs to be for all marks to line up right. now put the cam and caps back on and stick your finger in the tensioner hole and turn the motor over a revolution or two and assess the rotor and cam gear timing mark orientation.

never kick the motor over when orienting marks only do it by hand so you dont bend valves if you made a mystake

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dont even talk about a compression test fix your timing issue and confirm your exhaust valve clearances are corect

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I was confused by the 2 different sets of lines on the stator, but after checking and checking, the second line on the stator (right line aka Line T) is damn near perfect with the mark on the left case. 

My timing is dead on. 

Manual says exhaust valve clearance is .011 +/- .001

So with mine measuring .003, ya it seems a little tight, but the rocker does have a little wiggle room. So it's not the exhaust valves hanging up. 

 

I'm pretty confident when the old engine seized, it spun the gear on the cam a hair. Apparently this is a common issue. 

So I just ordered a stage 1 hot cam, and cam bearings.

Should be in by Saturday with 2 day shipping. Hopefully all goes well.

 

Also, manual says compression gauge should be 57psi at stock bore. 

I was at 49/50 psi. Assuming it's a new engine, and the rings/cylinder isn't broke in, is the reason for having a "lower reading"

Either way, at 49/50 psi the bike should of started.

Edited by AlotL1keVegas

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i guess i'm confused i thought i knew what i was talking about i hope it all works out for you.

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I ordered a new stage 1 cam, bearing, and a wiseco shim kit.

I pulled the fly wheel off, and the key wasn't sheared or bent. But i replaced it anyways. 

The timing isn't off? It's dead on. I was confused about the marks on the stator. It is timed to the right hash mark. 

 

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spark fires BEFORE tdc,  so the tdc mark is usually the 2nd mark.  Your .003 exh clearance might be effecting the decompresser timing, Check the clearance there too

 

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