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Muffler Mod & Carb Adjustment

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I finally got around to doing the muffler mod on my '07 TE250.

After the mod it would not idle. I adjusted the idle up to where it idles at about 2000 rpm but soon after dies.

When started cold with the choke it runs at about 5000 rpm, a lot higher than before the mod.

Any thoughts on how to get it run idle smoothly (which it did before the mod) would be appreciated.

Thanks.

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I didnt have any issues with mine before or after the mod. The only thing for me was that it Popped on decel more. No idle difference though. I did have to richen it up on the needle. all,s good. I dont know what to tell you. Never heard of this problem after an exhaust mod

mike

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I did the EX mod on my 07 TE250 and it ran fine with a small increase in torque although I wasnt that impressed. I cut it at about the middle of the taper and the two pieces no longer matched up well,so I heated the tube red hot and flaired it out with the ball end of a ball peen hammer to match the end cap correctly. I had a local welder weld it back on ($20.00). Its stainless steel. I really missed the lower RPM intake groan and the higher RPM bark. The power and low dbs, I feel are the best of both worlds. The final straw was when my buddy said it sounded like a Honda after I cut it...ugh!

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I seriously doubt that a simple muffler snipping would make a bike idle high. It might sound like it is idling high. All you are doing is unrestricting the muffler. Not taking it completely off. The only thing that it is changing is backpressure. Every engine something or other I have ever known would start and idle fine without a muffler. Its all the upper rpms that would suffer.

Mike

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I did not have any idling problem after the muffler mod. But I had already re-jetted my bike before I cut out the restrictor. If you did not re-jet and you still have the 50 pilot jet that's your problem. When you opened up the exhaust, the motor is flowing/drawing more air through the carb and therefore is drawing more fuel up through the pilot jet. Increasing the venturi effect through the carb. You need to go down to a 42 pilot or lower.

If you already re-jetted, then try leaning out the fuel screw.

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420 is correct. I have just recently done the "cut the gay baffle out mod" as well on my 07' SM450R. Here are my jet settings that Clark Mason suggested for an example:

DVP clip 5th from the top

42 pilot Jet

fuel screw 1.5 turns out

60 leak should be fine

Main Jet 182

Honestly I rejetted at the same time that I took the baffle out, cut the exhaust down 4.5" (like Dieselox), took out all the emissions stuff, AP cap removed, and throttle stop removed. I thought I would have to play with the jetting a little bit but it was spot on. Just a tad bit of pop on decel but I was very impressed with the power gain. It's feels like I was riding a donkey before now it's hard to keep that front wheel on the ground. Dieselox what did you do for the decel pop?

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I guess i didnt have the issue because i had already replaced my pilot jet with a 42 per the JD jetting instructions. I still have a slight pop on decel. Everyone that has heard it says it isnt nothing but it still bothers me. My settings are the same as yours Harv. Next im going to go with the JD blue needle. If that doesnt do it, im going to try different clip positions. I went to a 45 jet and it had a really bad bog at WOT from idle, and the bike ran with a smooth idle with the fuel screw all the way in (rich).

mike

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I run the JD Blue Needle with the clip at the 5th slot from the top with a 180 main jet. My pilot is a 38 and the leak jet is what came in the JD kit. I had a major bog until I leaned out the pilot to get a good idle then richen the needle until the bog went away.

As for the feel of loss of top end I think it's just that, "feel". Meaning- Now that the bike accelerates better overall from the bottom, you don't feel the surge of power as the motor reaches it's peak range. It's not slower on top , it's faster on the bottom so you don't have as much of a transition. Creating a flatter power curve , not less power , just a more steady accceleration curve.

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Again I agree with 420. I don't think it's a fall off in top end power more than it is a general improvement in the overall power curve. I never purchased the JD jet kit what is the "blue needle's" code and do you think that would help me out. I'm in almost the exact same boat as dieselox (maybe because I copied him with my exhaust). My bike really doesn't pop that bad, it's more like a gurggle/burp then a full on backfire type of pop, if that makes any sense. I did start to run out of gas the other day and it started poping and backfiring like hell and I thought I really f'ed something up but I was just out of gas oohps. Got to love the good ol reserve tank. Mine is the SM so my type of riding is a lot different than an MX version.

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I finally got around to doing the muffler mod on my '07 TE250.

After the mod it would not idle. I adjusted the idle up to where it idles at about 2000 rpm but soon after dies.

When started cold with the choke it runs at about 5000 rpm, a lot higher than before the mod.

Any thoughts on how to get it run idle smoothly (which it did before the mod) would be appreciated.

Thanks.

adjust the fuel screw

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yes Harv, Mine is the same sound. Its not really annoying, just not perfect.

DRZnXJnWI Quote:

Originally Posted by Pdm_2230

adjust the fuel screw

I adjusted the fuel screw to about 4 full turns and still no difference. Thats when i went to a bigger pilot (45). It bogged real bad.

When i called JD, they said the blue needle has a different tapper to the head. Thinner for richer. The needle jet works in the 1/8 - 3/4 throttle. I only get the pop just after i close the throttle from a high RPM. Not from a 1/8 down to 1/4 throttle. Ill probably drop a clip or two first to richen up the red needle before i completely change it.

It runs so well though. I hate to change anything. Im just looking for that perfect setting. Plus it keeps me tweeking on it.

From JD FAQ page:

Deceleration Popping on 4-strokes

The most frequent cause of loud popping on deceleration is an air leak at the header pipe connection to the motor. Even a very slight air leak can cause the deceleration popping. This is usually harmless, but can be annoying. As the pipe develops carbon/soot, the popping usually reduces with ride time.

The jetting can be adjusted richer at idle to help reduce the popping in most cases. A lean idle mixture can cause popping on deceleration, but the deceleration popping is usually more mild. Try turning the fuel screw on the bottom of the carburetor outwards by 1/4 turn steps up to 1 turn. The next option would be to switch from the Red marked needle (if currently being used) to the Blue marked needle in the same clip position (or 1 step leaner) to make the low-end jetting richer and keep the mid-range unchanged. Be aware that richening the low speed jetting excessively will reduce mileage and make the motor more difficult starting when hot. If your motor doesn't need the choke at all when cold starting, then the idle may be on the edge of a rich condition when hot.

Note that all the Japanese motorcycles have a bolted header flange and gasket to prevent exhaust air leaks. Yamaha WR450s and WR250s have a air-cut coast enrichener to reduce the same deceleration popping too.

Mike

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exactly- you did the right thing, he may or may not need to (we don't know what his jetting specs are).

If fuel screw is set "perfect" and is less than 1 turn out- I'd go smaller on the pilot- if fuel screw is set "perfect" and is more than 2.5 turns out- go bigger on the pilot. Fuel screw set perfect is when you turn it in to closed the bike stumbles- then turn out until idle smooths and peaks, I usually then turn it back in about 1/8 of a turn. Now that is the setting ideally- turn it all the way in and count the turns- you should be between 1 and 2.5 turns~~ if not change you pilot as above. If you turn it in and get no change go smaller if you turn it out and no change go bigger. Don't pick on me for saying "perfect" couldn't think of another way to put it:thinking:

Sounds like your bike is running great for you-:) That's the big test, not finding bogs or hesitation, surges.... I would not worry about some decel popping- usually its not jetting- but "can" be sometimes and so its mentioned. Usually for my bikes its been a leak at the head joint- fixed with some Permatex copper high temp silicone. The big concern with that air leak is you can pull in dust as it pulls in oxygen(which is causing the popping). What you don't want to do is over enrichen it to fix a symptom of something else.

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I agree completely. Those settings for the pilot and fuel screw are where i am sitting currently.

I have sealed all joints with Permatex Ultra Copper already.

I hope any of this has helped you Pdm_2230. We dont mean to hijack your thread.

I finally got around to doing the muffler mod on my '07 TE250.

After the mod it would not idle. I adjusted the idle up to where it idles at about 2000 rpm but soon after dies.

When started cold with the choke it runs at about 5000 rpm, a lot higher than before the mod.

Any thoughts on how to get it run idle smoothly (which it did before the mod) would be appreciated.

Thanks.

1. Are you saying it would just die after starting it with the choke on or off?

2. You had to adjust it to after warming up to operating temp. 2000rpm with the choke in?

3. Warmed up to op. temp., what is the lowest rpm it will idle at? (2000 ?)

If you adjusted the rmp to 2000 then pulled out the choke, it will go up higher.

As stated before, your idle sounds like it was close to good before. You shouldnt have to due much but fine tune it. There is another issue it sounds like.

What are your settings anyway?

Mike

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Thanks for all the responses and the refresher on jetting.

The bike idled before the mod, not at all after. I adjusted the idle up thinking that it would take care of the problem, but when starting cold with the choke it would run up to 5500 rpm or so - not right. When warmed up it would run fine but would not idle at all. Naturally, I thought the mod changed the jetting.

I needed to order a new fender and called the folks at Motoxotica. I mentioned the mod and the idle issue. He reinterated what most of you have said - the mod would not have this kind of an impact on the idle. He asked if the bike had been sitting for prolonged period. It had although I have had it out several times over the last few weeks. He recommended that I check the pilot jet. I pulled it out and could not see through it. I used a piece of metal guitar string (High E) to clean it out. I put back together, started it up and could not believe the difference. I am not sure it ever idled this smoothly and all decel popping is gone. :)

BUT - I can turn the air screw all the way in with no impact to the idle. Do I need to go with a smaller pilot jet?

Again I assumed that this was related to the mod. Now I need to pull the bowl and make sure that it is clean. The bottom of the cap that you unscrew to get to the jets had some residue in the bottom. Anything in particular that I need to pay special attention to when cleaning the carb?

Thanks.

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Pdm_2230

Glad Motoxotica helped ya...

Yes, clogged pilot will do make it idle poorly for sure...

started it up and could not believe the difference. I am not sure it ever idled this smoothly and all decel popping is gone.

BUT - I can turn the air screw all the way in with no impact to the idle. Do I need to go with a smaller pilot jet?

its a "fuel screw" not an air screw (2-strokes have air screws) and works with the Pilot (fuel jet)....

where does the idle peak at?- generally yes you should opt for 1 size smaller pilot- but even if it does not stumble when closed if its ideal seting is between 1 and 2.5 turns out- leave it...

if you completely unscrew the fuelscrew you should have a spring, washer, and then an o-ring (all small don't loose) and in that order. Make sure they are clean.

take off the float bowl- and take out the jets, you will have the main jet, starter jet (choke) probably a 65, and your pilot. Write doun the numbers enscribed on them. let them soak overnight in laquer thinner. If you have a leak jet inside the bottom of the float bowl cover write doun the size and spray the orfices.

I would take off the AP cover, ap diaphram on the bottom and clean the

orifices and enure the diaphram is in good condition. There's orings in the cover don't loose them.

Take off the top cover- and leave the slide where it is don't take out- turn upside down holding the slide in place- spray cleaner in and let it run out. There's a small nut in the center of the slide as you look doun into the carb- taht holds your needle in place- take out the nut and take out the needle inspect it for wear and clean it- write doun the numbers- or not the color (red blue) of the top, write woun the placement of the clip- (slot 4 from tip~)clean the top cover, spay the bottom orfices in the float area. Carefull not to bang or put pressure on the float- you could check the float height at this point too. (look for pictoral instrucitons on here) if you choose to.

Take off the airbel- (thing that connects to the air box flange) airbell may be the type that does not come off- but if it has two allen head bolts on the sides- it does take that off- carefull of the o-ring gasket, take out the 2 airjets (one main probably a 100) one is the Pilot air jet(probably a 60) put those with the other jets and soak- spray the orifaces and let drain.

reassemble- hopefully you paid attention and can put back together- but is easy.

Also if you let the bike sit for weeks or months- drain the float bowl- there's a screw nest to the drain, or turn off your gas and run it dry... That way you will have less problems with jets clogging due to gas evaporating in your floatbowl...:)

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Yeah it's all about fine tuning your jetting for your riding style and of course you should take the above mentioned steps to keep that carb clean. Yep Dieselox I know what you mean, not bad but not perfect. I'm going to try the Permatex Ultra Copper and see if that helps any because, I did add a few washers on the side of the exhaust to offset it from the rear tire rub. I did put a little hard setting Permatex gasket maker on the exhaust cap before riveting it back on to the can just in case, as well. If you have any luck with any different jet settings let me know Dieselox.

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Glad to hear you are back on Pdm_2230.

Motoxotica is a great shop.

DRZnXJnWI Put in a great write up of the carb breakdown. Post up your jetting when you get all the numbers please. Im always curious to what others are running. While you are in the carb, it is a good time to replace carb hoses and install a carb filter.

Also if you let the bike sit for weeks or months- drain the float bowl- there's a screw nest to the drain, or turn off your gas and run it dry... That way you will have less problems with jets clogging due to gas evaporating in your floatbowl

Good thing DRZnXJnWI posted. This is something alot of people forget. It will really help you in the long run.

B Harv ill keep you up to date on my trials. Everyone tells me to keep it where its at because it runs so good but oh well.

Keep us posted Pdm_2230 on how its running for you

mike

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Diesel I hear you there. I'm keeping mine where it is until someone can prove me wrong with a better setup. I rode it to work today and it ran pretty well. I run 100 octane what does everybody else run, as this could have a small effect on things. It does make it smell so good too....

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Ok, in an order to keep everyone posted like i said, im posting my findings.

As I stated in a few posts, i have a small pops on decel. Month ago I tried to go up to a 45 pilot and all i got was a horrible bog and stumble at idle to WOT. I turned the fuel screw all the way in with no difference in Idle or bike shutting off. Which tells me it was supper rich. The pop was gone though. Re-enstalled the 42 Pilot and no more stumble or bog but pops returned. So yesterday i tore into the carb and moved the needle clip down one position, (6th down from the top. JD instructions for kit is 5th down from the top). For those that dont know, the needle handles fuel delivery from 1/8 to 3/4 throttle. After several WOT runs from Idle and then closing the throttle, I still had maybe 2 to 3 pops on decel but not the 4 or 5. Next I turned the fuel screw out from 1.5 to 2 turns. After several more runs, i get only one pop. This was all at operating temp in 70 degree temps on pavement, (for max traction and load on the bike). I think i am good and happy. Here are my current settings:

Sea Level

Muffler Mod (restrictor pipe and 4" length of Muffler removed)

New Packing

All joints sealed

JD KIT

42 Pilot Jet

Red Needle (clip 6th position down from the top)

180 Main Jet

JD Leak Jet (dont know what size it is)

STEATH Racing Titanium Fuel Screw 2 turns out.

AP enabled with O-ring

Throttle stop removed.

NGK Iridium spark plug (nice brown color after runs)

I am really happy with it now. If i had anything else to try, The next thing would be JD blue needle (richer) clip in the 4th Clip position down from the top. The reason for the clip position is once you get to the bottom of your current clip, you go to the next richer needle. Middle clip position on the next richer needle is almost the equivalent to the bottom position of the leaner needle.

Like i said though, im happy and will only dig in again if i feel an itch.

Let me know if you have any questions.

Mike

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Hey Diesel, I run the blue needle at the 5th slot. It seems to run great with no popping. My pilot is a 38 though.

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