AIRHEAD VALVE ADJUSTMENT with Pics

I do....actually I have two sets---the'yre available at Advance Auto Parts ,and many others----

 

I now keep them in a sandwich bag with a bit of oil. The gauges started to rust...

 

Hello everyone, i have a few questions, first i hear that yamaha ( from a dealer ) shims are best compared to online shims is this true ? second lets say all is good timing, valves, sync. when/ how and why do you adjust the m( im not sure what you call them ) screws on top of the carbs that you start out at 2 1/2 turns ? Last Q, if you have 1 cyl, that is lower on combustion than the rest do you sync the others to that cyl ?

 

I think you need to start a thread for your bike. Put these qustions in that thread, as the answers will likely lead to you having more questions.

 

my bad. will do.

 

I have a 1982 xj 750 j maxim. My first question is i hear that yamaha ( from the dealer ) their shims are better than online shims is this true ? Next on top of my carbs the screw that you set at 2 1/2 turns out to start, then adjust... when do you adjust these? and how do you know if you have adjusted them right? What are the things you do before you start to adjust these screws? last Q If you have 1 cyl that is lower in combustion than the others do you use that one to sync the other carbs to?

 

if you want to pay 28$ for shims at the dealership go ahead,the after market shims are 8$ my dealership sells both.
problem is I have to buy the aftermarket shims in a 5 pack. so if my dealership sells both which is better?

I pick up new bmw shims when I see them on ebay.
there is a shim pool here of used shims which all work well.

the syncing is done to the lowest power cylinder

you can buy a color tune to adjust the mixture screws, or read the spark plugs by doing plug chops and adjust the screws. a temp probe works too.
you want your plugs to be paperbag brown.
you can adjust by ear if you want
as to when, you adjust screws sync ,adjust screws then sync .........

if you start your own thread in the tech forum we can go into detail about your bike and what you need to do after the valve adjustment

 

Thank you for this info my new friend, look for me in the tech forum.

 

Thanks for the thread. I took all of my measurements and so forth... then realized it's 30*F outside. I know you shouldn't check the clearance HOT but how cold is too cold?

 

Well... I believe the engine internally needs to be under 92 f , but I've never seen a minimum temp...... but I would think if my hands are too cold, I would wait till they are a bit warmer, and the metal isn't too COLD to touch--- lol

 

Great how to do the shims Fritz thanks.

 

As a rule of thumb, steel expands (or contracts) at a rate of 0.001 inch (0.0254 mm) per 100 degrees Fahrenheit. So checking the valves at 30ºF instead of 60ºF will not matter enough to cause trouble.

 

Does anyone know the highest mileage an XJ engine has done without an overhaul? What is the average life of a timing chain on the XJ 900f? My bike has only done 34000 miles.

 

You mean engine tear down?

I know of some reports over 100k..... my first 650maxim now has close to 60k on it.

All of my runners have around 30-35k......

Take care of clearances, oil, and keep carbs clean..... you'll not have to worry about tearing the engine down

 

I know of an Ariel from the late 30's that ran for almost 160,000 miles before an engine rebuild. Now add 50 years of improvements to engine manufacturing practices and oil characteristics.

 

Yes Hogfiddles I meant an engine stripdown. As you say routine maintenance is the best way to protect the unit. I have still to check my valve clearances but I cleaned the carbs as the engine would not idle when I got the bike now it's running great. Which oil do you recommend for the XJ. I used to use GTX years in my CB 750K2 (should have kept that bike) but not sure if that is ok for the XJ 900f. Yes k-moe that is a great mileage perhaps it was a Square Four? Going to change the oil and filter every 3000 miles anyway and next job is checking the shim cam clearance.

 

I use Yama - lube 10 W – 40 in all the bikes, all the time

 

See link in kmoe's signature about choosing the right oil for wet clutch motorcycle. All the stuff and more.

 

Stumbled across this thread and was very curious as to when it was recommended to check the shim clearances.
My 1982 750 has a minimum of 200,000 k on it and I am sure its over 300,000. The original owner ( I am second owner) told me he put over 100,000 k on it. I have turned the 5 digit odometer around twice myself.
The only work thats been done is front and rear brakes once and a set or two of spark plugs.
Oh and of course my awesome hand built custom exhaust.
In my opinion if its not broke dont fix it but dont want to have any unseeen catastrophic failures waiting for me.

 

Checks should be performed every 5,000 miles. Adjustments as-needed.
Not checking or adjusting the valves WILL cause things to break.
The first sign of trouble is usually difficulty restarting the engine when it's hot, but sometimes the first sign of trouble is a valve head snapping off and dropping onto the top of a piston and the engine making funny noises until it stops running.

Do you hear the valves ticking? No? Then they are in dire need of adjustment.