300 running issues
 

Hi guys
A friend has just brought a 300 57plate, it's got what I believe is a fuelling issues, the problem is 1st & 2nd it won't rev out. 3rd upwards it's about to come on the PV and it splutters horrible once passed it pulls well.
The PV is set ok and not seized. Has anyone suffered from this, and what did you do to solve the issue?
It feels like mid range fuelling,so I think a needle problem.

Thx in advance

Jon

This sounds dumb, but have you pulled the air filter and cleaned it? A long time ago I had a buddy who cleaned his filter but left a rag in the airbox, and it had the same issues.

hi mate

Plug,, cap could be reeds, blocked carb, crap in the tank
bad earth, coil, cdi
clean the carb and check nothing has come loose ie jets then pull the reeds as some times the corner breaks off.
start with the easy stuff and what's not going to cost as it may be a simple fix
then change the plug even if its a old known working one check and clean the wiring connections and clean the earth, I would put some oil on them like wd40
if nout change the coil and worst get the cdi checked

hope this helps

Hi
Yep air box is ok. Carb stripped and checked, new plug and cap, earths seem ok but will check with a meter.
Going to a dyno next week to check the fuelling, see what that shows

Check the silencer sounds like a blocked spark arrester. Just had this problem I have the Leo Vince silencer and the spark arrester screen was plugged. My bike ran the same as yours.

I've got the same problem with my 09 300 nambo. Only had it a week so hardly started work on it yet. It will be interesting to see how you get on.
Good luck.

+1, friends 6-day done the same thing.
Removed screen and just fine

Hmmmm. Opened up my exhaust and it was fine, so don't think that is the cause for me. The air filter was less than spotless though. Clean now and ready to try at the weekend.

Check your jetting, especially the needle. Remember it's been scorching hot in the UK lately, though it has cooled a bit now. If you are still on the stock N1EF or G needle it will be way rich. If you follow Jakobi's advice on jetting you won't go far wrong and you will get so much more from your bike. It's a quick and easy fix and well worth the effort. I put up with mine for a year and a half before I found this site and realised the standard jetting was all wrong. Less than 10 quid and 10 minutes work had the needle swapped and the bike transformed. I wouldn't waste time and money on dyno time, tuning for off-road is about response and feel from the the motor, not flat out WOT running. Just my tuppence worth.

Right. I've still got the N1EF in mine. DDK sounds good but not sure where to get one. Any recommendations and sources for needles?
Cheers

What year 300 is it? We have been running a 172 main, 40 pilot, and a n3cj or cw on the 2nd clip at around 3500 to 5000 ft. with good results. The stock needle that comes in them just doesn't seem to work here. They really load up in the quarter throttle range.

09. PWK carb. Running 178 main, 40 pilot and N1EF needle. 20 C and less than 1000 feet above sea level. The spring loaded pin on the float needle is compressed about 1/2mm when float seam is level with carb body. Clean air filter and exhaust. Very little slooge. Not too smokey at 50:1

Your local Yamaha/Suzuki/KTM dealer will sort you out with whichever needle you choose to go with. You may want to get a couple of different ones so you can compare them. I used an N8RH KTM needle simply because my local dealer had a spare one in his jetting box. It's still a tad rich but miles better than it was before. I could go a bit leaner with it but I'm happy enough at the minute so I will just leave it as is. There is a load of info on here and it takes a while to get your head round it all but stick with it and you will reap the benefits.

Thx for the response guys, my mate has now took it to a dyno were my ktm 250 was set up,which also uses the PWK carb, that had a power jet kit fitted to it, and it transformed the bike, it's a rocket now. Hope he can sort the gasgas out, I think the same will be done, as it is a similar issue to mine.

Ah the luxury of a dyno. Hope that sorts it.

Using the bung and tube method I have found my fuel level to be 1mm above the body/bowl seam. Could I take this lower, say to 2mm below? On some slow, steep descents I've noticed the idle drops and the motor stalls easily with extra smoke. I'm assuming the forward tilt of the carb combined with the downward angle of the bike is raising the fuel pressure in the carb. I'm using the bike for fairly gentle trail riding so not much WOT. Safe to go that low? :D

Ok. So I changed the needle to a NEDJ in clip 2. It has not cured the problem but I'm going to drop the main down to 172 next and see how that goes. Bike runs nice and smooth now with no burble/4 stroking at part throttle. However it is running hotter and pinks when you roll on and off small throttle openings. Also a marked reduction in bottom end torque. I'm going to raise the needle 1 clip and take it from there.

What sized pilot. Expect to use a 42 with the J diameter, and yeah go a clip richer. If thats too rich NECJ#3 will put you half way between the two.

The float heights are stock at 6.5mm but if you lower the fuel level another 1-2mm it will work much better.

PJ=40. Fuel level 2mm below bowl seam using bung and tube. I was hoping you would partake Jakobi. :D
The advice on here is excellent, and I'm enjoying the learning curve. Thanks guys.
I raised the needle a clip and I'm sure I've got back some bottom end grunt. It's very good and smooth, still a bit of pinking around very small throttle openings though. Need to change that pilot up from 40 to 42.

Changed to a 42pj and 172 main. I'm completely happy with the performance off road now (low to medium revs), lovely. The original problem is still there. Won't pull through a mid range flat spot with WOT but can be nursed through by closing to half throttle. When on the pipe she's away and pulls hard. These symptoms are aggravated by a period of slow riding and improve with a road blast. I wonder about leaning the main a bit more.

Have you check reeds allready?

Sent from Razr MAXX

I wouldn't go any leaner on the main. I was kinda thinking you are probably a little on the lean side all ready. I would think at that elevation you should be up around a 178 or 180 main. I really like that N3cj or cw needle. I would think with a 42 pilot and that needle in the third clip position you should be in the ball park. I am totally basing this off of what we run at our elevation so who knows I maybe way off. I think it would be worth giving it a try though.

A reed check is immanent ;)
Na I'm not going to go leaner. It was a daft idea.
Have noticed the spark cap was a bit loose, and on inspection is quite eroded and black inside.....
Also it's 5k ohm and I'm running a resister plug so no need for two suppression resisters. I'll swap it out and try again.

nah, best to leave suppression stuff in place these days of digital ignitions, you won't lose any spark performance.

Good call.
I changed the cap out (for a 5k ohm one :)) and put a new plug in. Still the same.
Reeds next.

I've just looked at the reeds and found the carb stub gasket was upside down so it shielded about an 1/8th of the opening into the reed block. That can't be good. The reeds looked ok, no frayed edges, cracks ect. Two of the outside petals were not sitting flat though. Maybe half a mm high so you could see a good chink of light through there. I was thinking of flipping them.

Reeds now perfect and gasket corrected. Flat spot fault still there. I tried increasing the main to 180 and it became much worse. Hmmm. Might try a 170.

I tried a 168MJ. Yuk. Flat spot still there but bike is too aggressive and pinks loads more. Didn't run it like that for long. :D

What spark plug are you using?

I've tried
BR8 EIX
and
BR8 EG

I have experience similar problems on my snowmobiles if I tried running non resistor plugs

I think these are both resister type plugs.

What needle are you using?

Currently an NEDJ
Previously a N1EF
Fault the same for both. It happens at WOT only so I'm thinking the needle may have less of an influence. The chap at Gas Gas UK said the silkolene oil I was using was bad for gumming so maybe I'll go through the pv again. Also the exhaust.

Mine had a giant hole in the middle of the power band with original needle, so I put a CCK needle in it.
That solved my issue.
You say yours has a flat spot on WOT (wide open throttle)??

Your reed cage isn't installed upside down is it? Sounds stupid but mistakes happen. The intake passage is offset to one side by a few mm. If it is installed this way it will not want to hit wot without a good bit of nursing

I wish it was that. Yeah it would be miles out of alignment upside down.

How do you know what is the right way up?

The hole in the reed block matches to the spigot the carb joins to (and is located off center in the reed block). Put it in upside down and the ports won't match, even though externally everything will.