2001 EC250 Jetting

[Gothicsera]

I'm sure I posted quite a bit here last year, but must have been my imagination. So hi everyone! I'm based in the UK and last summer I picked up a 2001 EC250 project which was in a poor way. It was burning a lot of transmission oil and had been used as a farm bike for a long time. It ran, but barely when I got it.

Long story short I did a full rebuild on the whole bike including the engine which I rebuilt with all new bearings, piston and cylinder. Boysen carbon reeds, new intake rubber, air filter etc.

I just got it road/trail legal here in the UK yesterday and I'm now trying to get it running properly.

Yesterday it wouldn't start hot without choke, with a 38 pilot and felt lean. Stepped it up to a 42PJ today and it now starts hot and cold nice and easily, first or second kick. But it's still not running great. I get intermittent "ding ding" like letting off the throttle and misfire at 30-35mph in 5th gear. It also feels flat at higher speed and WOT and doesnt seem to want to rev out, like its lean its not breaking up/crackling. But going by others jetting I'm already on the rich side.

It pulls well at low rpm on the trails.

AS1 PWK 38 AG carb with #7 slide
42 pilot
AS 1.5 turns out
180 main
N3EG needle, clip 2nd groove from top
FMF Gnarly pipe and power core muffler
0-500 ft
10-25deg C.

Motul 710 fully synthetic oil at 40:1

I have some other needles, N1EF and N0ZE and have ordered a 40 and 45PJ and 182 and 185 MJ. I have 178 MJ in my existing spares already.

I'm going to have more of a play on some local lanes tomorrow and see if I can do some more low speed testing and work through the whole set up from scratch. But am interested in any thoughts from you guys and experts.

Thanks
Sera

 

[(F5)]

You will need some industrial side cutters. Locate the N1EF and cut it into 3 pieces so you aren't tempted to use it.

Then pull the carb and with a magnifier or perhaps your phone and a light, inspect the needle jet. Any ovality will make it impossible to jet properly. As a farm bike it probably has a lot of miles and idling time.

 

[Gothicsera]

You will need some industrial side cutters. Locate the N1EF and cut it into 3 pieces so you aren't tempted to use it.

Then pull the carb and with a magnifier or perhaps your phone and a light, inspect the needle jet. Any ovality will make it impossible to jet properly. As a farm bike it probably has a lot of miles and idling time.

Thanks.

I should have stated I bought a used carb as the body on the one on the bike was really worn, both the needle jet and the float pin hole. the replacement looks OK, but I will check it again.

 

[(F5)]

Good.

N3EG should serve you well, if your gas is anything like ours. Try different positions. Try idle mixture screw. Then write down on a wall in your garage.

I will only think about throttle positions when jetting. Not revs.

Four times. Use big brush strokes.

In on the screw is richer. Out leaner. Then change a Piolt in that direction.

If it doest rev out on full throttle, smaller main.

If it gets bitchy and stuttery under load it's lean. If it gurgles its rich.


Go look at the writing on your garage wall again before Changing a jet.

 

[Gothicsera]

Good.

N3EG should serve you well, if your gas is anything like ours. Try different positions. Try idle mixture screw. Then write down on a wall in your garage.

I will only think about throttle positions when jetting. Not revs.

Four times. Use big brush strokes.

In on the screw is richer. Out leaner. Then change a Piolt in that direction.

If it doest rev out on full throttle, smaller main.

If it gets bitchy and stuttery under load it's lean. If it gurgles its rich.


Go look at the writing on your garage wall again before Changing a jet.

Thanks again.

I fitted a 178 main this morning before going for another ride.

I've now marked the throttle in 1/8 increments on the grip, so I can see exactly where I am.

At a steady speed in 3rd gear with the throttle barely cracked its stuttery - so lean?

From a steady speed in third with the throttle barely cracked, opening to 1/4 throttle it still stutters a bit before cleaning up as the rpm rise - so lean?

From a steady speed in third with throttle barely cracked, opening to half throttle it pulls clean but doesn't seem to rev out, doesn't stutter just feels like it hits a limiter - so rich?

From a steady speed in third with throttle barely cracked then opening quickly to WOT it almost lifts the front wheel and then again feels like it hits a limiter too early, but to that point it pulls clean. So rich?

A 38 pilot was too lean and it wouldn't start hot without choke

From the above;
I am guessing the 42PJ is still too lean so I will try a 45.
I am guessing the 178 main is still too rich so I will try a 175.
I will adjust the clip position once I've found a main that works better.

Seems to idle best and rev cleanly with a tiny crack of the throttle with the AS 1.25-1.5 turns out.

 

[Zman]

I think your plan make sense and you are on the correct path. I think a 175 main should be closer but you may also try a 172. What slide do you have?

Setting the float level is critical. Make sure both individual floats are aligned with each other on a flat surface before you set the height in the carb. After you set the float level make sure the carb is level in the bike. It can be kind of difficult since the carb is mounted on a complex angle relative to the bike. I find it easiest to put the bike on a stand, with the tank off and use a level across the hoop/ tank portion of the frame to make sure the bike is straight first then I use a level across the top of the carb with the screw cap top off.

 

[Gothicsera]

I think your plan make sense and you are on the correct path. I think a 175 main should be closer but you may also try a 172. What slide do you have?

Setting the float level is critical. Make sure both individual floats are aligned with each other on a flat surface before you set the height in the carb. After you set the float level make sure the carb is level in the bike. It can be kind of difficult since the carb is mounted on a complex angle relative to the bike. I find it easiest to put the bike on a stand, with the tank off and use a level across the hoop/ tank portion of the frame to make sure the bike is straight first then I use a level across the top of the carb with the screw cap top off.

Thank you. I'm now waiting for more jets to arrive. I've ordered all sizes from 170-185 mains and 40-48 pilots. My other bikes are all in that ball park anyway so they will be useful for those anyway.

The carb float level seems good and the floats are aligned. It doesn't leak at all if the fuel is on and the bike is upright. If you lean the bike over it will dribble a little. Carb is level in the frame too.

I'll swap one jet out at a time so I know where I am. Will try and get the low throttle openings sorted first.

 

[(F5)]

It can be hard to tell the difference between rich and lean stuttering, the only description is lean is more bitchy, like it means it. Try one way and if doesn't improve, try the other.

 

[Gothicsera]

It can be hard to tell the difference between rich and lean stuttering, the only description is lean is more bitchy, like it means it. Try one way and if doesn't improve, try the other.

Thanks. It's better with the 42 PJ than it was with the 38, so I'm guessing I'm going the right way. The stutter is very obvious and constant. 30-35mph in 3rd is terrible.

 

[Gothicsera]

OK, so I bought a load of genuine Keihin jets as the jets in the carb were unknown age and brand.

Fitted a 45 PJ and it ran terribly, back to a new 42, better but still sputtering at very low throttle constant speed. Now back at 38 and it's better again and seems to start OK hot or cold. Still a bit of a sputter, but maybe it's as good as it will get. AS best at 1.25 turns out. Throttle response from closed to 1/8 throttle is clean. I think I'll run it with the 38 for now and see how it behaves on the trails.

Clip position 3 was a little sputtery at 1/8-1/4 throttle. lowered needle 1 clip position to lean out and it's clean at midrange now.

Main now 180, from 178. Might try 1 larger again as a plug chop (clean new plug) was still a little pale on the plug for my liking.

 

[(F5)]

Um, so you didn't have a 40pj? Plug chops are a technique thing, and only valid if you do them right. And only really for mainjet. Long straight, wide open for several seconds, pull clutch, kill engine, coast to stop.

180 is huge for a 250, but might be right for a 250, I really don't know. Local petrol and altitude, blah blah. .

 

[Gothicsera]

Um, so you didn't have a 40pj? Plug chops are a technique thing, and only valid if you do them right. And only really for mainjet. Long straight, wide open for several seconds, pull clutch, kill engine, coast to stop.

180 is huge for a 250, but might be right for a 250, I really don't know. Local petrol and altitude, blah blah. .

I've got a 40 pj on the way but it hasn't arrived yet.

Ref the plug chop that's what I'm doing. I'll do it again over the weekend.

Honesty I just want it running nicely on the trails, easy to start hot and cold and safe in terms of not being lean.

I've lots of 4 stroke tuning experience, but not so much 2 stroke, so it's a learning curve. Appreciate your inputs, thank you.

E10 fuel, 40:1 100% synthetic oil, sea level and approx 10deg Celsius ambient.

 

[(F5)]

With E10 Is assume you would need very slightly richer than petrol straight.