What is wrong with my GN250?

[ABBA]

I recently purchased a 2007 GN250E with 2000 k's on the clock for commuting to work. I got a friend to look at it for me as I was out of the country at the time and didn't want to miss out on the deal. When I got it I found it has a problem, it sort of dies/surges and plays around when taking off and dies/surges a bit when cruising along at normal around town speeds. I have pulled the fuel tap out of the tank and cleaned the filters etc there, pulled the carb off and fully stripped it down and blown it out with compressed air and checked and cleaned both the the air cleaner and spark plug (also checked plug gap), I've also checked for leaks in the all of the seals going from the air filter box to the carb and then to the head. Nothing I have done has fixed the problem, it has only made it a bit more rideable. Has anyone out there had similar problems/issues with their GN??? Help!!!

Stephen

[Hiflyer]

maybe its the oil? my hyosung had the same problem for a bit but thats cos there wasnt any oil in the tank haha, not something that was on my checklist. so yea, might just be something you didnt think shold need checking?

[ABBA]

Hi, thanks for that...no not the oil sorry, that was one of the first things I checked before my first ride...Cheers

[rogson]

Check the mixture screw (top/front of carb under a rubber plug) - should be 4 turns out.

[ABBA]

Thanks for that, I've got it set at one and half turns out. Is that the specified setting? I'll try that out tonight and let you know how I get on. Cheers

[rogson]

Don't know what the spec setting is. See below for how I got to 4 turns.
http://www.kiwibiker.co.nz/forums/showthread.php?t=78169&highlight=User+friendly+GN250

[Racin Jason]

All of the new GN250's have this problem.
The mixture is not set right for Zealand conditions and it runs lean, causing a miss or splutter at low rpm and needing a long warmup period with the choke on. this cannot be fixed by simply adjusting the mixture screw.

when new, Suzuki dealers are "supposed" to correct the problem by fitting a larger pilot jet. But i believe these are no longer available. however since then some dealers have been drilling the original pilot jet to the correct size.
All Suzuki dealers should know all about this.

Also make sure the fuel hose from the tank isnt kinking - common problem

[ABBA]

Jason, thankyou so much for that information. As much as I hate to do it, I will contact the local Suzuki dealer and see if I can get this issue sorted. I will let you know how I get on. Thanks again!

[ABBA]

Hi Jason, well I rang the local Suzuki agent and they had no knowledge of the issue with the pilot jets at all. Can you let me know the name of the Suzuki dealer that you know of that has delt with the problem and I will contact them.

[idb]

Check that the fuel tank vent is clear.
The way I would do this is to disconnect the hose from the tap and run it into a container, after 30secs or so open the fuel cap and see if it increases in flow.
Make sure your bike is cold when you do this just in case you splash some about!

[Bass]

Hi Jason, well I rang the local Suzuki agent and they had no knowledge of the issue with the pilot jets at all. Can you let me know the name of the Suzuki dealer that you know of that has delt with the problem and I will contact them.

My wife's GN had the same/similar problem from new. Basically the idle jet/passages were blocked and they are quite tricky to get at with the compressed air. In the finish, we took it back to the dealer and told them what we had done (I asked them first before I got stuck into it as I didn't want to void the warrenty). Basically, I had done everything that they would have and so they just replaced the carby.
The problem returned again shortly afterwards, but cleared itself after a short while.
It happens again every time the bike is left standing for any length of time but usually clears again within the first km or 2.

I can only suggest that you try the compressed air again but concentrate on the idle passages. They take a bit of tracking and they emerge as 3 or 4 tiny holes just where the edge of the throttle butterfly contacts the barrel wall when the throttle is closed.

There is an idle jet insert in there, but it takes some finding.

[ABBA]

Hi, thanks for that advice...I spent quite some time with blowing out those passages you spoke of, plus every other passage again tonight with no further success...I do wonder if a prior comment was correct about the pilot jet as it is very small (it has the number "38" on it). If anyone could give me the correct size for this jet and where to get one it would be much appreciated, Cheers!

[kiwi cowboy]

Hi, thanks for that advice...I spent quite some time with blowing out those passages you spoke of, plus every other passage again tonight with no further success...I do wonder if a prior comment was correct about the pilot jet as it is very small (it has the number "38" on it). If anyone could give me the correct size for this jet and where to get one it would be much appreciated, Cheers!

Just blowing it may not do the trick.
You may need to soak it in white viniger and then wash in hot soapy water ,rince ,dry and blow with comprested air:msn-wink:

[Conquiztador]

Visit a local bike wrecker, get a s/h GN 250 carbi from one of the Jap models (not the Chink ones!!!) and swap. Problem solved. Cost you approx $100 - $150. Good luck.

[LBD]

The mixture is not set right for Zealand conditions and it runs lean, causing a miss or splutter at low rpm



Sorry mate, dont know where that came from but its Bollocks....Air fuel mix (Lean ness) is not geographical except where altitude comes into play, (2000m plus) Sea level in NZ, Japan, New york or london all has the same atmospheric pressure (and air density) Temp can also play apart, but NZ is not the hottest or coldest.

If you remove the fuel line off the carburetor and open the fuel valve, a steady stream of fuel should flow.

Then check the float level that controls the availability of fuel to the jets, going by the symptoms, to me it sound like it is to low.

Cheers

[ABBA]

Hi, cheers for that advice...I checked the float level and fuel flow from the tank previously but I'll have another look at it and report back...this is starting to become a bit of a mystery to me!

[Hiflyer]

maybe you shouldnt have a GN :P kidding haha

but it sounds like there is an optical illusion or something going on here! haha post updates!!

[joshy28]

im having the same problem...around 3 - 3500rpm is when most of my splattering happens, and dont get me started on the mornings... i also need to have the choke on all day just to take off in 1st..... however, i can ride all day on the motorway with no problems...

when i first got it, it showed small signs of splattering but after 2 months, its a big problem all through the gears....

[Racin Jason]

Sorry mate, dont know where that came from but its Bollocks....Air fuel mix (Lean ness) is not geographical except where altitude comes into play, (2000m plus) Sea level in NZ, Japan, New york or london all has the same atmospheric pressure (and air density) Temp can also play apart, but NZ is not the hottest or coldest.

If you remove the fuel line off the carburetor and open the fuel valve, a steady stream of fuel should flow.

Then check the float level that controls the availability of fuel to the jets, going by the symptoms, to me it sound like it is to low.

Cheers

No Its not bollocks, many new bikes suffer from this problem. The reason is the quantity of oxygen is the air in/around new zealand is greater and the air in asia and also cleaner. There are service scedules in place for some carby bikes that get carried out in the predelivery inspections so the problem is corrected before the customer gets the bike. This was put in place by Suzuki new Zealand, which just happens to be in my home town of wanganui.

I know this because i am a suzuki mechanic and i have done the chinese GN 250 modification myself many times. The VS650 is another one we have to change. Unfortunately this problem was not realised straight away so there are a few spluttering GNs out there.

[Racin Jason]

Jason, thankyou so much for that information. As much as I hate to do it, I will contact the local Suzuki dealer and see if I can get this issue sorted. I will let you know how I get on. Thanks again!

I work for whitelock suzuki in wanganui, we have a jet drill we use, not sure of the exact size thou, ill try to find out tomorrow.

I have riden them before and after drilling the jet, from brand new, to see the difference. It is quite noticable. I found i had to rev it fairly high and ride the clutch quite a bit to get away in first before the mod.

[Metalor]

I have a smilar problem with my TU250. It started sputtering and surging like it does when it's running low on gas which I then just flick to reserve... the last couple of days it'll be running fine then I'll back the revs off a bit and it'll start doing it! The only thing that helped was opening the throttle right up.

Really weird, I assumed the carb would just need a clean out or something....
Only happens at motorway/highway speeds. What do you guys reckon?

[LBD]

No Its not bollocks, many new bikes suffer from this problem. The reason is the quantity of oxygen is the air in/around new zealand is greater and the air in asia and also cleaner. There are service scedules in place for some carby bikes that get carried out in the predelivery inspections so the problem is corrected before the customer gets the bike. This was put in place by Suzuki new Zealand, which just happens to be in my home town of wanganui.

I know this because i am a suzuki mechanic and i have done the chinese GN 250 modification myself many times. The VS650 is another one we have to change. Unfortunately this problem was not realised straight away so there are a few spluttering GNs out there.


Gotta be some Suzuki excuse/cover up for a different problem....

Oxygen % in the air is near a constant 20.7% globally. Air density can change according to altitude or slight weather influenced barometric pressure variances.

Atmospheric pollution is only noticable to the human body because of the toxins and other nasties in the air. An internal combustion engine will not notice this...

Exactly what is the GN 250 modification you write of...Larger main jet or smaller main jet. I would suggest the mod is more to manage differing quality fuels globally then any atmospheric variations....

Okay Honda/Yamaha/Kawasaki/Ducati and other mechanics, you want to chip in?

[ABBA]

No Its not bollocks, many new bikes suffer from this problem. The reason is the quantity of oxygen is the air in/around new zealand is greater and the air in asia and also cleaner. There are service scedules in place for some carby bikes that get carried out in the predelivery inspections so the problem is corrected before the customer gets the bike. This was put in place by Suzuki new Zealand, which just happens to be in my home town of wanganui.

I know this because i am a suzuki mechanic and i have done the chinese GN 250 modification myself many times. The VS650 is another one we have to change. Unfortunately this problem was not realised straight away so there are a few spluttering GNs out there.

Hi there, thankyou for that useful information. Can you please give me some pointers as to how I can remedy this matter/get the modification done? I am in Christchurch and have tried the local Suzuki dealer who had no knowledge of this issue at all and no idea how to fix it. Thanks in advance!

[Racin Jason]

OK got some solid info for you, sorry couldnt find the manual to get the actuall jet size. Talked to our senior technican to make sure this is correct.

For new (chinese) GN250

Change the pilot jet to the next size up.
Not available as genuine suzuki part, but aftermarket is available to order from any bike shop(mikuni i think).

If the bike is still a little hesitant, and espcially if you ride in town alot or short trips while the engine is cold - you can raise the needle 1 position. ( that is move the clip on the needle down 1 slot.)

This is what we have found works well, and customers have been satisfied with the results.

Of course if a GN didnt have this problem from new and it has developed since then, then this will not fix it. Most likely you have blocked jet or something like that.




Oxygen % in the air is near a constant 20.7% globally. Air density can change according to altitude or slight weather influenced barometric pressure variances.

Atmospheric pollution is only noticable to the human body because of the toxins and other nasties in the air. An internal combustion engine will not notice this...

Exactly what is the GN 250 modification you write of...Larger main jet or smaller main jet. I would suggest the mod is more to manage differing quality fuels globally then any atmospheric variations....

Okay Honda/Yamaha/Kawasaki/Ducati and other mechanics, you want to chip in?


Well i am not a scientist so i can only relay what has already been writen, and i would be interested to know about what, if any problems other dealerships have.

As you say im sure it is partly the design/manufacture of the bike which is at fault. The thing is we have trouble with a few models and we are the only country in the world that seems to have these problems. (again according to suzuki japan.

Most of the time its only very slight problem, (most people dont even notice it) a 1/2 turn on the mixture can make it idle a bit better. others need bigger pilots and higher needle settings but thats about it. the problem bikes seem to run only slightly lean at the low throttle opening, and go fine when wide open - so the starndard main jets are always fine. We usually find these things out fairly quickly because SNZ is only 1/2 km from our shop and they often work with us to sort things out.

[SS90]

Hmmm, not so sure about the quantity of oxygen at sea level in N.Z compared to the quantity of oxygen at sea level any where else in the world...I'm pretty sure it's always the same, sea level, is sea level, in my opinion.

BUT, you are correct on the solution to the problem!

However, All CARBED motorcycles come from the factorys nowdays with tiny little pilot jets. This is for emmission standards.

A new Harley Davidson, when it come into NZ has a small pilot, you must remove the one the bike comes with, and fit a larger one.

Harley's use a mikuni carb.

Well, they did 5 years ago.

If the dealer doesn't change the pilot at the P.D.I, the bike surges, and farts around at low operating speeds....

the pilot jet is too small!

If your GN has a 38 pilot jet, I suggest going to a 40, or even 42 pilot.

Take the original as a sample, go into Superior Motorcycles, and see if they have one in those sizes, as they quite often have pilot and main jets for Mikuni and Kiehen in stock.

Also, perhaps even consider "shimming" the needle on the slide 0.5 mm...... The new GN's are set up VERY VERY lean for emmisions standards all over the world, NZ has to suffer the problems caused by the E4 standards compliancy.... as that is where all bikes are now designed to comply.

[ABBA]

Thankyou to all those that have contributed...I finally think I've got all the info I need to sort the problem here in ChCh. I'll let you know how I get on after I get the new jet and make the required changes. Thanks again!