[maddog681]

Hi, the new guy here – just bought a 98 Rebel 250 after I persuaded my wife to let me back on a bike after my last crash/stay in hospital/six months of work etc. Can’t ride the thing yet due to my injuries but plan to spend the next few months turning it into a bobber, I am thinking of getting rid of the air box and putting a pod type air filter on, from what I’ve read I believe the increased air flow will cause the bike to run lean, and the way to fix this is to re jet the carbs, which all sounds a bit complicated to me, I’m not really after any increase in performance but I just like the look of the pod air filter, I was thinking if the bike is running lean with a new air filter instead of re jetting the carb could i not restrict the airflow from the filter instead, thinking of some form of metal plate between the filter and carb, into which I can drill various holes to fine tune the airflow to what it was with the original filter, what do you think? Would it work? Hope this all makes some kind of sence!!! Let me know what you think.

 

[cagie]

Welcome!

This isn't aimed at you but I'm still having a hard time understanding why changing an air filter will make anyone have to re-jet. Someone who is more knowlegible might have to fill in the blanks here. BUT, here are my thoughts:

Changing the air filter does not increase air flow. How can it? the same amount of air is drawn by the engine whether it is a stock air filter or a piece of tissue paper, unless the filter is clogged, but reduction of air intake is another problem. An air filter should be able to deliver whatever the engine requires, no more, no less. Any airflow restrictions are found further into the system, like the carb intake holes, etc.

IMO, the airflow issue comes into play if you change the exhaust system. Notice I said exhaust system. That, to me, would mean changing the engineered system. The engineers factor everything together when designing a system; how much total air flow goes through a system. Changing the system would require chainging other components of that system to keep it in check. i.e. changing jets to compensate.

From personal experience, I changed to a K&N filter and changed muffler. Notice I said muffler, not exhaust system. The headers are the same with the stock pipe size at the start of the muffler. No backflow was changed, but I get more resonance and some burble on deceleration (not backfiring). I did not rejet, and to my knowledge thus far have had no ill effects, able to leap tall buildings with a single twist of the throttle (I jest, but do run well on the interstate), great gas mileage, etc...

 

[flitecontrol]

Welcome to the forum. Hope your injuries continue to heal.

 

[cagie]

BTW, the water problems where due to the pod being outside of the frame and aimed wrong. I have since tucked it back up against the eingine and have had no more problems.

 

[GearJammer]

On the Classic Rebels ('85, '86, '87) it seems that most are able to alter both air filter and exhaust without having to re-jet (tho' a few owners feel a need to re-jet) I believe Cagie's is an '87, yes ? and mine was an '85.......I removed the stock airbox, installed an aftermarket foam air filter, replaced the mufflers with EMGO Shorties, no re-jet, same as Cagie.

On the '86 450, I've kept the stock airbox, but am running EMGO Shorties and it didn't require a re-jet.

Seems I remember that the later 250's ('96 & up ?) had to re-jet if changing out BOTH intake and exhaust and this may be due to the later Rebs being set even leaner in their stock form from the factory. BUT.......I would think that if one changed only ONE aspect, either air filter OR exhaust, but not both, you probably would not have to re-jet, simply keep an eye on the plug reads.

 

[maddog681]

Thanks for the info

Cheers everyone for the quick replies, seems like it would be worth trying just fitting a pod filter and see what happens, I'm all for a simple solution, just didnt want to break my new toy!!! will give it a go and let you know how it goes but it may be a while before I get to give it a run out, can't wait, the rebel seems like a great little bike, I had a honda cm125 about 25 years ago and had loads of fun on it riding all round the Highlands of Scotland in the ice and snow, exciting!!!! but a little cold !!! but then I was a lot younger then, The rebel seems to have improved on the CM in all the right ways without losing the good bits, heres to summer days and long rides....