Conflicting information about exhausts

[dmb5450]

Hello everyone, I was doing a great deal of research on this forum as well as some others, and even on random websites. I have found conflicting data on what exactly needs to be done if I install a slip on exhaust.

I am considering a Two Brothers slip on. I have read the following:
1. Just install the exhaust and you ear ready to go
2. Install then rejet and or shim the needles
3. Install then after a decent distance ride, check the spark plugs, the color will indicate if further maintenance is required.

Now I have read that some exhausts will indicate that nothing more than an install is required, while others will give more instructions. I’m not sure if this is the reason for the varying information I have found.

I appreciate any help anyone is able to offer.
Donnie

[edxmon]

Originally Posted by dmb5450

Hello everyone, I was doing a great deal of research on this forum as well as some others, and even on random websites. I have found conflicting data on what exactly needs to be done if I install a slip on exhaust.

I am considering a Two Brothers slip on. I have read the following:
1. Just install the exhaust and you ear ready to go
2. Install then rejet and or shim the needles
3. Install then after a decent distance ride, check the spark plugs, the color will indicate if further maintenance is required.

Now I have read that some exhausts will indicate that nothing more than an install is required, while others will give more instructions. I’m not sure if this is the reason for the varying information I have found.

I appreciate any help anyone is able to offer.
Donnie

The truth is that no 2 bikes are the same. Some bikes come lean from the factory some come rich. Until you ride with the slip-on installed and feel the bike you wont be able to tell what you need or need not do. An exhaust allows an increased flow of air and makes the mixture a bit lean, thus why some people shim or jet. Checking the condition of the sparkplugs after riding with the slipon will let you evalutate whether you are running rich or lean.

tldr; There is no ONE RULE TO RULE THEM ALL when it comes to slipons on these bikes, that's why you have "conflicting" information

[LoD575]

Will probably need to shim. Look at removing the kleen air system if backfiring/popping issues are present.

If in doubt install slipon and ride then check plugs for running condition.

I am running slightly lean with my current setup of dan moto slipon, snorkel removal, pipercross air filter, kleen system removed, and 2 washer shim.

I plan on adding another washer but looking at jet kits as well.

[alex.s]

slipon doesnt change ex.gas flow very much.

[mustang5.0]

modifications work best with a tune

[alex.s]

you should get a full pipe and a jet kit instead of the slipon.

[edxmon]

Originally Posted by alex.s

you should get a full pipe and a jet kit instead of the slipon.

If you can afford it, do this.

Otherwise I think there is still a used DanMoto Jisu in the Marketplace section of the forum for under $100.

[dmb5450]

I thank you all for the quick response and input. Is there anyway of knowing before installing the slip on if the bike runs lean? How do you know it is running lean after the install? If the bike runs lean and nothing is done to correct it what are potential problems that could occur?
Sorry for all the questions, I just want to make sure I am understanding everything.
Donnie

[edxmon]

Originally Posted by dmb5450

I thank you all for the quick response and input. Is there anyway of knowing before installing the slip on if the bike runs lean? How do you know it is running lean after the install? If the bike runs lean and nothing is done to correct it what are potential problems that could occur?
Sorry for all the questions, I just want to make sure I am understanding everything.
Donnie

A lean condition is the end result of too little fuel and too much air. Slightly lean conditions create drivability problems. Lean mixture burns hotter. Worst-case scenario: Lean conditions can and do destroy engines. Holes in the pistons, burnt valves and trashed main bearings are the direct result of lean mixtures.

Rich mixtures are the end result of too much fuel and too little air. Rich mixtures waste fuel, contribute to carbon buildup and pollute the air.

Typical Lean Conditions:
- Poor acceleration; the engine feels flat.
- The engine won't respond when the throttle is snapped open, but it picks up speed as the throttle is closed. (A too-large main jet also mimics this symptom.)
- The engine runs hot, knocks, pings and overheats.
- The engine surges or hunts when cruising at part-throttle.
- Popping or spitting through the carb occurs when the throttle is opened. Or popping and spitting occurs through the pipe on deceleration with a closed throttle.
- The engine runs better in warm weather, worse in cool.
- Performance gets worse when the air filter is removed.

Typical Rich Conditions
- Engine acceleration is flat and uneven and loses that "crisp" feel.
- The engine "eight-strokes" as it loads up and skips combustion cycles.
- The engine's idle is rough or lumpy, and the engine won't return to idle without "blipping" the throttle.
- The throttle needs to be open continuously to maintain acceleration.
- Black, sooty plugs, a sooty exhaust pipe and black smoke from the tailpipe that stinks of unburned fuel.
- Poor fuel economy.
- The engine works better when cold. Performance falls off as it warms up or the ambient temperature rises.
- Engine performance improves when the air cleaner is removed.

Thanks to MotorcycleCruiser.com

[alex.s]

Originally Posted by dmb5450

If the bike runs lean and nothing is done to correct it what are potential problems that could occur?

less power. you will heat up the spark plugs and valves more than they should eventually leading to damage.

[bdavison]

Just remember running rich is always a better option than running lean. Running rich just gives you poor performance, running lean destroys engines.
Running it lean, even for a short ride, can burn a hole in a piston and reek havoc inside your engine. Don't risk it.

So I'd recommend raising the needles with at least one washer. If you find that its running too rich, then you can drop it down. If it runs good, then get a jet kit and rejet it properly.

I'm personally of the opinion that raising needles alone is a half @ssed way of adjusting a carb, since it only adjusts the mixture above idle...everything in the carb should be adjusted with jets AND needles to create an ideal mixture across the ENTIRE range. Not using a combination of jets and needle adjustments can result in lean at idle, and super rich at cruising RPM mixtures. Which equates to lousy performance and added stress on the engine.

[alex.s]

Originally Posted by bdavison

Just remember running rich is always a better option than running lean. Running rich just gives you poor performance, running lean destroys engines.
Running it lean, even for a short ride, can burn a hole in a piston and reek havoc inside your engine. Don't risk it.

So I'd recommend raising the needles with at least one washer. If you find that its running too rich, then you can drop it down. If it runs good, then get a jet kit and rejet it properly.

I'm personally of the opinion that raising needles alone is a half @ssed way of adjusting a carb, since it only adjusts the mixture above idle...everything in the carb should be adjusted with jets AND needles to create an ideal mixture across the ENTIRE range. Not using a combination of jets and needle adjustments can result in lean at idle, and super rich at cruising RPM mixtures. Which equates to lousy performance and added stress on the engine.

i think the belief that "shimming" needles alone is a good idea comes from a misunderstanding of what the needle actually does.


there are two flows of fuel running through the carb. the idle jet and the main jet. the idle jet ('pilot jet') is always on and always lets the same amount of fuel through. as you increase vacuum through the carb, the slide begins to open because of the vacuum from the engine. the more the engine is pulling (higher RPM, less resistance from throttle control) the more that slide will open. the slide is connected to the needle. this needle slides up and down with the slide. the needle goes into the needle jet oriface which then is metered through the main jet. the needle has a minimum fuel allowance of nothing obviously, and a maximum that is the amount the main jet lets through.

changing the level of the jet with things like clips or washer 'shims' changes how quickly the needle opens the main jet. so this means if you 'shim', or raise your needle, at lower vacuum, the needle has less obstruction on the main jet, and you get more fuel down low. up high in the vacuum range, the needle opens up completely before you hit the top of the vacuum range. what this means is you stop adding extra fuel when you need more fuel. so now, by shimming, youve made the low end richer, and the top end leaner.

[dmb5450]

Originally Posted by edxmon

A lean condition is the end result of too little fuel and too much air. Slightly lean conditions create drivability problems. Lean mixture burns hotter. Worst-case scenario: Lean conditions can and do destroy engines. Holes in the pistons, burnt valves and trashed main bearings are the direct result of lean mixtures.

Rich mixtures are the end result of too much fuel and too little air. Rich mixtures waste fuel, contribute to carbon buildup and pollute the air.

Typical Lean Conditions:
- Poor acceleration; the engine feels flat.
- The engine won't respond when the throttle is snapped open, but it picks up speed as the throttle is closed. (A too-large main jet also mimics this symptom.)
- The engine runs hot, knocks, pings and overheats.
- The engine surges or hunts when cruising at part-throttle.
- Popping or spitting through the carb occurs when the throttle is opened. Or popping and spitting occurs through the pipe on deceleration with a closed throttle.
- The engine runs better in warm weather, worse in cool.
- Performance gets worse when the air filter is removed.

Typical Rich Conditions
- Engine acceleration is flat and uneven and loses that "crisp" feel.
- The engine "eight-strokes" as it loads up and skips combustion cycles.
- The engine's idle is rough or lumpy, and the engine won't return to idle without "blipping" the throttle.
- The throttle needs to be open continuously to maintain acceleration.
- Black, sooty plugs, a sooty exhaust pipe and black smoke from the tailpipe that stinks of unburned fuel.
- Poor fuel economy.
- The engine works better when cold. Performance falls off as it warms up or the ambient temperature rises.
- Engine performance improves when the air cleaner is removed.

Thanks to MotorcycleCruiser.com

wow, thanks for such a full answer! That really helped. I appreciate everyone's help. I feel much more knowledgeable about what I was researching.
Sincerely,
Donnie

[GeneJunkie]

250s generally come from the factory lean for the mpg numbers or was it for the emissions standards (been awhile since I cared and I don't recall anyone have a rich running newgen 250 from the factory, mine was lean).

Get a full system. The TBR slip on is going to cost you almost as much (if not more depending on the type you get) as an AreaP full system. If you are already going to open up the carbs to shim for a slip on, its not that much different for the full system. There are many people on this forum who haven't used a jet kit for a full system and only have done shimming. I think if you go through the jetting database there are a couple of members have written exactly how much they shimmed instead of using the jet kit.

The slip on will just be a noise box, you will NOT see an improvement on performance (I have the dyno's to prove it). If you want the noise, more power to you.

[leed]

Originally Posted by GeneJunkie

If you want the noise, more power to you.

No pun intended, right?

Also: Alex, I think (might be wrong) you mean to say that the top end fuel mixture remains the same from shimming (as a result of "max fuel" still being limited by the size of the main jet).

[GeneJunkie]

Originally Posted by leed

No pun intended, right?

haha, I didn't even realize that until you pointed that out