POD Filter Re-jet

[Guest]

I know this is a tough one but I have a Suzuki GS 125 with a VM style carb and just removed the air box (not for performance but because of the look I'm going for) and I put a POD style filter on and took it for a ride expecting nothing but trouble as I haven't changed the jet and I experienced NONE of the running lean symptoms. No bogging, idles beautiful, starts from cold no problems, no popping on decel and the spark plug is tan in colour. Could this be possible without a re-jet? Basically I asked my mechanic and he said that I shouldn't need to re-jet...what do you guys think?

[fastbob]

Well it must be possible because its just happened to your bike. It's a bit surprising, you would never get away with this on a CG125 . So,happy days and on with the rest of your project. Could be a different story in heavy rain though.

[Guest]

Yeah it's just something I'm experimenting with but I don't know enough to be taking carbs apart etc. I'm going to take her out tonight again tonight and ride it a little harder and see what it's like when I'm doing 60-65

If it did need a re-jet I'm assuming it would be very noticeable

[Guest]

Also didn't realise that you're in Coventry fastbob I'm only down the road. Are you any good with tuning bikes etc, could do with someone to help if I get stuck but don't want a garage ripping me off

[fastbob]

The thing about small cc single cylinder four stroke bikes is that they either work or they don't. There isn't really much you can do to tune them other than compensate for any modifications to the exhaust or air box. I used to buy and sell cg125s which are fairly similar to a gn125. All I know is that they were extremely sensitive to air box / filter modifications. There is a little plastic shroud about the size of a fag packet that sits around the air intake. Leave this off and the bike will only run at speed with the choke half on. SO ...fitting a pod filter to a gn might not be a great idea whatever jet size or carb settings you use. Let us know how things turn out.

[Guest]

Hi mate

So far with the pod on and crankcase breather on the bike seems to be running exactly the same as before if not a touch better. She doesn't rev like she's going to blow up when I'm doing 50-60mph and I get much more out of 4th than I used to. It starts from cold first time like before and I have absolutely no popping on decel at all. She also idles smoothly and seems very responsive to all throttle positions. The only time there is minor hesitation is in 4th but it was exactly the same with the air box so not sure what that is (maybe it's just how I'm riding)

I've also checked the spark plug after every ride and it's a nice tan/biscuit colour

Based on all that info would you say it seems ok?

She sounds so much better now too

[fastbob]

From everything you say it sounds just fine,happy days.

[Guest]

Well I took it out today and it started fine, warmed up fine, idle was fine, I just noticed slight hesitation at completely full throttle but if I roll the throttle on slowly and gradually it's better and doesn't hesitate as much. When I say hesitate it doesn't bog completely or struggle it just mildly hesitates for like a second and then might do it once for a split second but then it climbs up fine

I've attached a photo of the spark which I hope is visible. What do you think?

Someone who has the same bike as me has a 102.5 jet in his but he has a completely different exhaust where as mine is the stock. My jet is a 95...do you have any thoughts?

Thanks again

[fastbob]

When you say full throttle I guess you mean full speed which means lots of air swirling around the exposed pod filter. This turbulence can create differences in pressure that can have a negative effect on the carburetor. This is why the manufacturers surround the air filter in a carefully designed plastic box. Don't get me wrong,pod filters do look great but if bike makers could save a few quid by not fitting an air box they probably would.You will just have keep experimenting in the hope of getting it right. Worth bearing in mind that K&N filters can cause problems if you don't put the correct amount of oil them. An alternative to a pod filter is a foam filter that might be less susceptible to turbulence.good luck.