20 Most Recent 2004 Yamaha SR 400 Questions & Answers

Hi,

Sometimes the flywheel key can shear
putting the ignition timing off.
The inside of the flywheel can
rust causing problems.

a compression check will tell
you if the valves and engine
are okay. This is always the first
thing to check.

Is the fuel running through
the carb okay if you open the carb
drain screw?

Sometimes the fuel can have water
in it and needs to be drained
and new fuel added.

Check the spark plug cap as these
are known to have problems.

Carbs have to cleaned very thoroughly
to get all the passageways clean.

Is there a good flow of fuel to the carb?

Will it start on a spray of starting fluid?
Is the air filter and air box clean?

Sand any rust off the flywheel magnet surface
and check that the coils are
not rusted either.
You will need a puller to remove the flywheel.

Clean any ignition connector plugs you
can find with electronic spray.


Let me know,once done.

Hope i helped you.

Thanks for using ' Fixya ' and have a nice day!!

Here you go...around $79 from Yamaha at their site
http://www.yamahapubs.com/

Hello, you will find that the seal between the gearbox and motor is leaking, check your gearbox oil, it should be getting close to coming out of the gearbox breather (over full), do not ride, you will damage and burnout your gearbox.

You should purchase a gasket and seal set, pull your motor out of the sled, disassemble the motor, and replace all the gaskets and seals. You can purchase a piston kit on line that should come with pistons , rings , gaskets , and seals.The main problem you are having is an air leak on one or both of the crank end seals. Usually the clutch side seal leaks first. If you continue to drive you will probably score one or both of the cylinders.When you have the motor apart clean your carburetors and replace your spark plug caps. NGK has new plug caps for about $5 each. If your cylinders look good i would consider doing a light hone job and ring replacement. Again if you just buy new aftermarket seals pistons and gaskets you should be able to do a complete rebuild for about $150. Then your engine will be good for another 25 years. If you are limited on funds Just replace the crank seals , clean the carburetors, and put on new NGK plug caps (about $30).

There is a good topic about it at blasterforum.com

I do not know of a r 25 not likely could be , but do not find any info, the picture is a r250 i hope i have helped/

Take a look at the schematic here....

http://www.bikebandit.com/houseofmotorcycles/1981-yamaha-motorcycle-virago-xv920rh/o/m7932

It shows all of the components and the order in which they go in. If the one you are talking about is on the backside, they are fairly easy to put in. There is a spring holding it in place, I believe that spring is on the inside part (if you take yours apart you will find out) so when your cylinders move they create a vacuum pulling that in and allowing gas to pass by. use a little gasket sealer to hold it in place if you need to. And i mean a LITTLE sealer. You don't want excess to slip by and get into your carbs, that would not be fun to clean them for a little thing like that. Goodluck.

Bruno

ur kicker may be bad or the compression, fuel delivery, or ignition is failin

I'd be glad to help you with this problem.
There is no way to tell with out taking it to a shop to get put on a dyno.,Or you could have someone drive next to you telling you your speed at each wanted RPM's and gears.

If you have any question press add a comment in upper right corner or email me at [email protected] for a faster response.

Thank you
Premium FixYa Team

In a piston engine the compression ratio is the ratio between the volume of the cylinder and combustion chamber when the piston is at the bottom of it stroke, and the volume of the cumbustion chamber when the piston is at the top of it's stroke. Imagine a cylinder and the combustion chamber with the piston at the bottom of it's stroke. 900 cc of air in the cylinder and 100 cc in the combustion area just above the piston when it is at the top of it's stroke. That gives you a total of 1,000 cc. Therefore the ratio is 1000:100 or broken down a 10:1 compression ratio. Click the links to learn more. http://www.familycar.com/engine.htm
http://www.2carpros.com/how_does_it_work/engine.htm
http://auto.howstuffworks.com/engine1.htm
http://www.metacafe.com/watch/689942/how_a_car_engine_works_3d_animation/

hi you could try carlsalter.com and if there is one there you can download them for free