I've got an aftermarket exhaust. How to replace jets and unifilter installation?

[eSOL]

Hi guys,

Recently picked up an after market exhaust and was recommended to install bigger jets as well as replace the air filter with a unifilter. Just wondering where I'd pick up the larger jets and if anyone knows of a place that would install the unifilter and jets as I don't have much experience with engine adjustments.

Bike is a 1990 Honda Cbr250rr mc22

[hayd3n]

gets your jets from the government or have they scrapped them??
and the uni filter
find your local university :wacko:

[ducatilover]

Get jets from this fellow
http://www.trademe.co.nz/Members/Listings.aspx?searchtype=SELLER&member=106097
I would recommend buying several sizes. Or just get a shop/friendly local KB member to do it for you

You'll need to remove the tank/carbs.
May as well clean them, clean fuel filter and sync the carbs while you're there


The first step, however, is figure out if it's lean or not.
You'll get flat spots where the power just goes away when lean and backfiring/popping when you get off the throttle

Being a CBR I expect you'll have flatspots at 3-4000rpm, 8-9000rpm and somewhere above 12 is the usual for them with a free flowing muffler.

[AllanB]

Feck it man - stick the pipe on, go for a run and do a plug check to see hows it is running. Old school. Adjust to suit if you find it lean.

[Dragon]

Feck it man - stick the pipe on, go for a run and do a plug check to see hows it is running. Old school. Adjust to suit if you find it lean.

Also pays to run it on 95 :p

[Haggis2]

Make sure the jets are E marked or you'll be non LAMS compliant :innocent:

[sketch]

Make sure the jets are E marked or you'll be non LAMS compliant :innocent:

pfft and there guna no how?

and isnt a 250 automatically lams approved regardless of mods?
"Motorcycles and scooters with an engine capacity of 250cc or under are automatically LAMS-approved, with the exception of a small group of 250cc motorcycles are not approved for learner and restricted riders due to their high performance capabilities."

[ducatilover]

pfft and there guna no how? They sniff the exhaust.



and isnt a 250 automatically lams approved regardless of mods?


No.

[sketch]

[QUOTE=ducatilover;1130537048]They sniff the exhaust.


Bahahahahaha :killingme

[FJRider]

pfft and there guna no how?

and isnt a 250 automatically lams approved regardless of mods?
"Motorcycles and scooters with an engine capacity of 250cc or under are automatically LAMS-approved, with the exception of a small group of 250cc motorcycles are not approved for learner and restricted riders due to their high performance capabilities."

Are you feeling particularly slow today ... the :innocent: smiley indicates sarcasm at it's most obvious ... <_<

[FJRider]

Feck it man - stick the pipe on, go for a run and do a plug check to see hows it is running. Old school. Adjust to suit if you find it lean.

I agree ... putting such a muffler on a 13 year old 250cc motorcycle is unlikely to make much difference to performance or engine management. Probably as much difference to using 95 instead of 91 fuels.

[Dragon]

I agree ... putting such a muffler on a 13 year old 250cc motorcycle is unlikely to make much difference to performance or engine management. Probably as much difference to using 95 instead of 91 fuels.

My Gsx250 (2002) is all factory and is meant to run 91 however I suspect the carb has been tuned for 95 becasue at 9k+ it pings on 91 and I only run it on 95 now even if it does smell alittle rich (would rather rich then lean)

Plugs arent showing it running hugely rich but I can smell it

[FJRider]

My Gsx250 (2002) is all factory and is meant to run 91 however I suspect the carb has been tuned for 95 becasue at 9k+ it pings on 91 and I only run it on 95 now even if it does smell alittle rich (would rather rich then lean)

Plugs arent showing it running hugely rich but I can smell it

Running with a dirty air filter will make it run rich. To my knowledge ... running 95 instead of 91 wont make it run rich.

Tuned for 95 .. ?? :scratch:

[ducatilover]

My Gsx250 (2002) is all factory and is meant to run 91 however I suspect the carb has been tuned for 95 becasue at 9k+ it pings on 91 and I only run it on 95 now even if it does smell alittle rich (would rather rich then lean)

Plugs arent showing it running hugely rich but I can smell it

Change your plugs and set the gap correctly. It shouldn't pink on 91.
Are you reading your plugs correctly?

[Dragon]

Brand new air filter
Brand new plugs

I even pulled up the below to confirm I was reading the plugs right

http://suzukitu250x.blogspot.co.nz/2011/06/do-you-talk-to-your-plugs.html

on 91 read it as hot/lean

95 reads ok - cold/rich

no idea whats going on but again id rather run 95 and have it run rich then hear it pink at high rpm

[ducatilover]

Brand new air filter
Brand new plugs

I even pulled up the below to confirm I was reading the plugs right

http://suzukitu250x.blogspot.co.nz/2011/06/do-you-talk-to-your-plugs.html

on 91 read it as hot/lean

95 reads ok - cold/rich

no idea whats going on but again id rather run 95 and have it run rich then hear it pink at high rpm
That link isn't telling you shit :msn-wink: This, however, is good http://www.4secondsflat.com/Spark_plug_reading.html

If you're running lean or hot, I'd say your plug temp was wrong for the set up, which means something needs to be changed.
Jetting and mixture settings.
Dirty slides.
Plug gaps.
Plug leads
Valve clearances
Exhaust leaks.
Ignition timing (but it's non adjustable on a GSX, unless you slot the timing pick up holes and I doubt this'll fix the actual issue)

Does the bike pop and fart when you get off the gas at high revs and engine brake?

91/95 does not change you air fuel ratio, what you're seeing is (if it's actually pinking) the 95's ability to resist pinking.


Ninja edit:
Have you synced the carbs? If not, do this first.

[Dragon]

That link isn't telling you shit :msn-wink: This, however, is good http://www.4secondsflat.com/Spark_plug_reading.html

If you're running lean or hot, I'd say your plug temp was wrong for the set up, which means something needs to be changed.
Jetting and mixture settings.
Dirty slides.
Plug gaps.
Plug leads
Valve clearances
Exhaust leaks.
Ignition timing (but it's non adjustable on a GSX, unless you slot the timing pick up holes and I doubt this'll fix the actual issue)

Does the bike pop and fart when you get off the gas at high revs and engine brake?

91/95 does not change you air fuel ratio, what you're seeing is (if it's actually pinking) the 95's ability to resist pinking.


Ninja edit:
Have you synced the carbs? If not, do this first.

Am using Factory spec plugs havent changed heat range however so may look into it

Plug gaps are good, plug leads may need looking at however so will pull them off and test resistance when I get a chance

No popping or farting at all on either 91/95

I've never been that involved with carbs

Cant find any exhaust leaks, carb setting etc and valve clearences all got done recently (its been doing it since I got it)

no difference in power bike runs fine just hear pinking at higher revs while on 91 unless im imagining it

[FJRider]

no difference in power bike runs fine just hear pinking at higher revs while on 91 unless im imagining it

What percentage of your riding time is at "Higher Revs" .. ??

[eSOL]

What percentage of your riding time is at "Higher Revs" .. ??

So just looking at a unifilter on ebay ($60 holy shit). Picked up some jets from the trademe guy.

Anyone know if the motorcycle doc would be ok with installing them? Or can recommend a place to have these installed?

[FJRider]

So just looking at a unifilter on ebay ($60 holy shit). Picked up some jets from the trademe guy.

Anyone know if the motorcycle doc would be ok with installing them? Or can recommend a place to have these installed?

What indications or facts do you have ... as to the actual sized jets you require. Even if the size is just a guess ... is it just your guess, or somebody that has re-jetted a bike with the same modifications .. ???

And after fitting said jets ... what tests do you intend to do/get done to confirm it is the correct jet sizes .. ??

[eSOL]

What indications or facts do you have ... as to the actual sized jets you require. Even if the size is just a guess ... is it just your guess, or somebody that has re-jetted a bike with the same modifications .. ???

And after fitting said jets ... what tests do you intend to do/get done to confirm it is the correct jet sizes .. ??

Have been searching the net and came up with this on http://mootavic.olilolo.com/mods/tune.html

Will probably get the carbs cleaned(not sure if they need to be rebalance as i just had that done a few weeks before i got the slip on exhaust) and adjust the fuel mix judging by what ive found online.

[ducatilover]

So just looking at a unifilter on ebay ($60 holy shit). Picked up some jets from the trademe guy.

Anyone know if the motorcycle doc would be ok with installing them? Or can recommend a place to have these installed?
$60 is cheap.
Yes, the motorcycle doc will probably do it in his sleep. But you need to work out exactly how much of a change you need in jetting


Am using Factory spec plugs havent changed heat range however so may look into it

Plug gaps are good, plug leads may need looking at however so will pull them off and test resistance when I get a chance

No popping or farting at all on either 91/95

I've never been that involved with carbs

Cant find any exhaust leaks, carb setting etc and valve clearences all got done recently (its been doing it since I got it)

no difference in power bike runs fine just hear pinking at higher revs while on 91 unless im imagining it
Just run it on 95 then, costs bugger all more :niceone:
If you're getting little tiny white or silver flecks on your plugs, then it's pinking.
You could be imagining it though because the ignition timing is backed off in the higher revs, I'd say it'd be more likely to pink under load at mid-way in the rev range