1981 Yamaha sr250

.Dave.

New Member
Hello all,
I am new to the forum but I have been looking over a bunch of SR builds here and the inspiration is flourishing. I have a 81 sr250 that I bought a few months ago as a commuter bike and have high hopes for it.

SteveG, your tracker named Mexico is really what kick-started my immense interest in this style bike. I want to thank you and many others for sharing and giving me an insight on what these little machines can be.

Now I am new to the building game and I will have loads of questions that I hope everyone can help with as they come up. First one being about the air box... Ugly thing it is. I would love to get rid of it, But I hear it will cause me problems. What can I do? (may I add that the bank is light right now)

Anywho, here she is...
Not much to look at now, I know, but I hope to change that soon.
 

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Welcome Dave.
Spend some time reading up on what works and what doesn't and get to work!
 
Welcome Dave, I will be watching your build with keen interest.

As for the airbox, the main problem I have is with side winds. When I am hit by a side wind I can feel a loss of power as air is being drawn past the intake rather than into it. Also back winds increase my idle rpm, all because of the velocity stack.

If I were to revisit my SR I would build plate aluminium side covers and use a k&n air filter. Lucky for me the new owner plans to have me do this at his expense.
 
Thank you for taking interest, Brodie. I have read quite a few of your comments on this situation and it is very helpful. I like the idea of the aluminum side covers especially since the sr's airbox is quite restrictive to begin with and that would cut down on some airflow and I don't know a whole heap about jetting . I also saw what looks like a plastic cover to go over the pod filters? I wonder how that would work also... I have seen some builds using the UNI filter, are those a bit more restrictive?

Here's an example of the plastic cover I came across
 

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The stock airbox on an SR250 is very restrictive, but I don't think the answer is to throw a pod on there and then restrict that just as much. Rejetting is not difficult but may take a little trial and error. Once I rejetted my SR250 after switching to pods and less restrictive (but not wide open!) exhaust, it ran great and fast.

I had open sides like Brodie, but unlike him I never really had loss of power with side winds, but I also never really had it in a place that had serious side winds -- I guess location matters too.

Fun bikes, good luck with it!
 
Brodie said:
If I were to revisit my SR I would build plate aluminium side covers and use a k&n air filter. Lucky for me the new owner plans to have me do this at his expense.
Subscribed!
My current plan is similar to Brodie's suggestion - but to retain the OEM airbox and filter (no need to re-jet, easy to maintain air filter, no worries about rain, easy to convert back if desired, no real loss of performance) and plan to hide it by creating either aluminum or ABS sheet plastic side panels with oval number plates attached as I am raising the tail of the OEM tank (to be more level) and using a H-D "flat tracker knock-off" seat to continue that line.
 
Uni filters are just as good if oiled right, problem is most of the time they have more oil in them then the clutch does.

Have you thought about running the stock air box with some holes drilled in it to make it less restrictive? You should be able to get a high flow filter to fit it.

I can see the plastic covera for the pods preventing airflow just as much as the stock box.
 
Yes I am also thinking about keeping the OEM airbox instead of a pod filter. I live on the coast in Florida and we get sick ocean cross winds and lots of rain and a pod filter may not be the best choice im guessing. Also I love that open look of losing the box. I need to come to a happy medium.
 
ferget about the open look keep the stock airbox be happy with a good running bike
or do you want to be all the other sheeple that sacrafice performance for how they think a bike should look while parked
? are you man or sheep ?
besides when you are riding the bike the open look disapears
 
I sure as hell would have kept my airbox, if my SR came with one. I have the same problem with ocean winds and rain.

If you drill some holes out of the box, only small ones, and fit a less restrictive header (stock hs a smaller pipe on the inside) you will have a great running bike.
 
xb33bsa said:
ferget about the open look keep the stock airbox be happy with a good running bike
or do you want to be all the other sheeple that sacrafice performance for how they think a bike should look while parked
? are you man or sheep ?
besides when you are riding the bike the open look disapears
Good point. Those crappy side panels do have to go though (barely hanging on anyhow)
 
Brodie, I'm glad you share my struggle ☺ I am strongly considering keeping the box now. I just need to figure out how to make it look better too
 
Meh, let the dude continue to cry about the "open triangle" but regardless, the stock airbox is so restrictive you might feel a bit more pull if you rejet the carbs and fix the exhaust. The stock exhaust on those things is ridiculous. Like I said, mine got dialed in pretty easily and ran great for as long as I had it. I agree some stock setups are worth keeping when possible, I'm just not so sure about this one.
 
Several ways to hide the OEM airbox/battery (and, yes I know some of these have foam air filters :p):
P1050152.JPG

street-tracker-3-large.jpg

yamahamt04flattrack.jpg

yamahaflatstreet.jpg

Just takes some imagination and metal/fiberglass work.
 
Okay so I got swamped with work and remodeling my house lately so the Yami was neglected I put the airbox/filter dilemma on the back burner for a bit and got rid of that massive taillight and installed a new (for me) one. It is actually an old flasher off of my father-in-law's HD that I rewired, built a bracket to mount and installed. I like it...
 

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Some more progress... Took out the airbox (I know...) and put this together. It's an air conveyor coupled with my filter. It takes the incoming raw air and smooths it out for nice flow into the carb. So far it's actually running very well. Battery box is next...
 

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I love non-conventional solutions to old problems! Nicely done! Can you give more specifics on your conveyor? Google isn't much help.
 
Joe Suzuki said:
I love non-conventional solutions to old problems! Nicely done! Can you give more specifics on your conveyor? Google isn't much help.
Thank you. It's a Nex Flow Ring-Vac Pneumatic Conveying System. It has an inlet for pressurized air to flow but I just put a little filter on and the regular incoming airflow goes through jets in the conveyor and the bike seems to love it. I found this piece in the "graveyard" of obsolete parts at work
http://www.nexflowair.com/air-conveyor-standard.php
 
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