Need help from the 2 smokers

[green machine]

My mate ditched his WR250 for a YZ250(brand new).... and just rang me pissed off cause his bike gave him grief today(plug kept fouling)he's running 32:1 as per manual with that high octane Shell petrol.
Can any off you 2 stroke gurus offer any tips as per fuel mixture,air/fuel screw setting etc or any thing you might think basic but would be helpful to a 2 stroke virgin.......for the record he loves the bike(especially in the bush)but he was muttering that he should have stayed with a four stroke............hahaha

[telliman]

bet you he's running yamalube oil, have heard nothing good abt that oil, always fouling plugs!

[Rupe]

when it's talked about having a lean or rich 2stroke, its not the amount of oil you put in. It is the fuel and air mixture, so if you added more oil there would be less fuel making it a leaner mixture in effect. Having said that you should run a good fully synth oil at yamaha's recomended ratio as this is unlikley the problem.

He needs to try to work out where the enginge is bogging or feeling thick and make an adjustment there and go from there. It could also just be the air screw.

He also might need to run a gear lower and let it rev a bit more.


For a more infored answer Reckless really knows his stuff

[charles23]

bummer he didn't even get out of 1st gear...........missed out on a good ride, JAM Track rocks.

[B0000M]

40:1 is a good ratio, never had any problems at this ratio. dont know the yammmy specifics for jetting tho

[green machine]

bet you he's running yamalube oil, have heard nothing good abt that oil, always fouling plugs!

yeah he is.....i suggested a change of oil as i have another mate who was running Slkoline and 95 and kept fouling plugs.....changed to Motul 800 and 98 and hasn't had a problem since

[FROSTY]

Id suggest he basicly needs to clear its throat a bit. and hey Im running yamalube with NO issues at all

[barty5]

bummer he didn't even get out of 1st gear...........missed out on a good ride, JAM Track rocks.

Off topic what this track like these days years since i have been there??

[B0000M]

i suggest castrol tts, available anywhere -eg repco or supercheap or most bike places, cheap, reliable (15 years worth with no issues) and never a foulded plug

[jt119]

were is the jam track

[vr4king]

i suggest castrol tts, available anywhere -eg repco or supercheap or most bike places, cheap, reliable (15 years worth with no issues) and never a foulded plug

2ND that...........Have they recently changed its packaging i went to supercheap and bout some but was in a gold bottle?

[Dent]

Just re-read your original post. He just purchased it brand new right?

Well jetting out of the box, float levels etc are often not perfect on a new bike. I had my gasgas rejetted by the local expert after one day of running it in. I also had the float level adjusted, so it didnt piss fuel out the overflow when on the sidestand - yes it was that bad.

I would suggest he talk to the dealer, specifically the mechanic at the dealer who has the most experience with that model and jetting them right.
Or, ask on here about where to take it to get it jetted. DIY jetting on a brand new bike may not be his cup of tea.
As people have already said, the jetting must be right for the oil type and ratio used.

Also, whats the deal with needing, or thinking you need 98 on a low(ish) compression 2 stroke? Possibly a topic for another thread.

[scott411]

the Yamaha dealer should have had a base jetting spec if they were bad from new, some models are, and sometimes it depends on what market spec we get in this country, (euro spec tend to be a lot richer),

[t3mp0r4ry nzr]

agreed that yamalube is a`shit as its name suggests! but if he's having consistant issues with fouling, then look at riding techique if the jetting is close. maybe try leaning the pilot screw a lil

[B0000M]

Also, whats the deal with needing, or thinking you need 98 on a low(ish) compression 2 stroke? Possibly a topic for another thread.

detonation isnt cool, and if its anything like a cr250 - detonation will occur using shit fuel

[LittleJohn]

I would suggest that you look at the jetting and using good oil like Motul. If the jetting is standard and you are using decent oil then you could try and adjust the jetting and air screw.

As for changing the oil ratio be carefull with this. I have always been told by our local (very good) dirt bike mechanics to always run the manufacturers oil/fuel ratio and to change other things to stop fouling. I have just re-done a piston on someones bike that was only around 15-20 hours old. They were running a richer mixer (more fuel in ratio) than manufacturer had said. The piston was burnt right through, had burn marks around the outside of the piston and underneath the piston (where the pin goes through). There was also scratch and scrap damage done to the piston and the cylinder bore and slight burn damage done to the crank. Luckily we only had to replace the piston and give the cylinder a hone, but this was very lucky. Was just about new or re-sleeved bore, new crank and new piston to be done.

On the flip side I also know of people who do use different ratio's with no problem, suppose it depends on the rider.

Another option is to change your spark plug to a standard instead of racing plug, the standard have more tolerance to oil before getting oiled up.

My 5 cents worth anyway.

[Dent]

Out of interest I looked at a few spec's for the yz250 (these are 2006).
Compression ratio is higher than I thought they would be.


Engine type Liquid cooled 2-stroke, gasoline
Cylinder arrangement Single cylinder, forward inclined
Displacement 249 cm³ (8.76 lmp oz, 8.42 US oz)
Bore × Stroke 66.4 × 72 mm (2.614 × 2.835 in)
Compression ratio 9.2~10.9 : 1 (For USA and CDN)
8.9~10.6 : 1 (For EUROPE, AUS, NZ and ZA)
Starting system Kick starter
Lubrication system Premix (30 : 1)( Yamalube 2-R)
Transmission oil Yamalube 4 (10W-30) or SAE 10W-30 type SE motor oil
Periodic oil change 0.75 L (0.66 Imp qt, 0.79 US qt)
Total amount 0.80 L (0.70 Imp qt, 0.85 US qt)
Air filter Wet type element
Fuel type Premium unleaded gasoline only with a research octane number of 95 or higher
Tank capacity 8.0 L (1.76 Imp gal, 2.11 US gal)
Carburetor Type/ Manufacturer PWK38S/KEIHIN
Spark plug Type/Manufacturer BR8EG/NGK (resistance type)
Spark plug gap 0.5~0.6 mm (0.020~0.024 in)
Clutch type Wet, multiple-disc

[krad_nz]

Well if he's only ever had 4t's he probably just needs to adjust his riding style?

Rev it, keep it in the power band etc. Try riding it a gear lower than if you were on your 4t.

Assuming the jetting etc is all sweet of course.

[REDRIDER]

Had a guy a work who brought brand new KAWA 2T had exactly the same problem, went back and forth from the bike shop trying to sort it, changed to MOTUL problem disappeared. wierd...

[chop]

is it splutering off the bottom end?

[green machine]

Cheers for the help fellas..........all sorted.Went to Thunder X yesterday and sorted it out...we think he was mixing too much oil,he had 250ml in 8 litres....spoke to a fella there on a YZ 2 pinga and he said put 20-25 mls per one litre......done that and the rocket was away............he was a happy man.Can't believe how light it is,got blown over by the wind twice

[Dent]

Sounds like 50:1 to me, which is what I run with sythetic oil on my gasgas (as per the manf). 20ml per liter is 50:1.

For 32:1 he was right with 250ml per 8 liters.

http://www.csgnetwork.com/oilfuelcalc.html

[jt119]

lol it was a cr250 me with the sore hand nice bikes like watching you guys

[green machine]

lol it was a cr250 me with the sore hand nice bikes like watching you guys
Were you in the van up the top mate?......my mate with the 2 smoker said he asked you.....i was on the K-waka and spoke to a guy down in the bottom carpark............glad he got it sorted tho.....he was starting to regret his purchase but he's happy as a pig in s##t now.....was a bit of fun up there alright with not many kids around

[jt119]

ya your little guy was grate to watch he was going really well and ya that new yz looked like alot of fun guy said it was light as