valve adjustment idea...

tried searching on here and couldn't find my answer. i was laying in bed the other night and wondered if anyone made adjustable lifters for these types of motorcycles. i mean one that is threaded inside so all you have to do is turn one end to make it shorter or longer. much like an older car engine or racecar engine.

nothing against the shim method but it seems kinda chinsey and more work than what its worth. having to hold the valve open and change the shim. where as all you would have to do is turn a little nut and not touch the valve.

its just an idea and may not work. i have a 82 xj550 maxim. also working on a 81 suzuki gs850g (dont get mad, it was almost given to me) and would be interested in a set for it too since the engine is very similiar in design.

 

Honda Nighthawks of the same era had hydraulic (self-adjusting) lifters.

Adding "adjustability" would also add weight to the valve train, and limit RPM. That's the advantage to the "shim over bucket" system.

 

the shim arrangement is a much more precice method of controling valve clearences,
i take it you mean the rocker and tappet arrangement ?.
theres much less moving parts involved in the shim way,
screw ajustment would not work ,as the cam presses directly onto the end of the valve stem via the shim.
stu

 

here is a pic of a performance set for a 350 chevy. you can kinda see what i mean. but i guess there may not be enough room for something like this

 

I have a 2.0L Toyota motor with the system you describe, locknut and adjuster to change clearance. You can't get the same precision with those as with the shim. I feel confident that my XJ's clearance is within 10% of what I measure it as, I would say the truck motor is within 25% of what I measure. The cause is the spring loaded tappet arm and the tendency of the lock nut to move the adjuster, they put a little ambiguity into the mix.

I owned a Nighthawk 650 with hydraulic adjusters. I never had any problems with it, but it was a heavier bike and required hydraulic fluid for the clutch. If anything had gone wrong it is more expensive to fix.

 

ive adjusted valves on race engines with the setup as pictured to get one more inche of much needed vacuum. i can get it to stay within .0005 inch (half thousandth). not bragging but its actually quite precise.

maybe its just because im new to the shim idea and never done it before...

 

Shim/bucket setup was cheaper to make

 

Yep. OR you can really beef up the valve springs. Then parts wear faster

 

bigger cam and stiffer springs is also an option for the XJ... lol

only the numbers i found dont impress me much

 

Not surprising.

You will find that the XJ series was very well designed to begin with, performance wise. Yamaha basically gave us a "racebike for the street" and as such, there isn't much that can be done to "improve" performance. Most mods end up taking something away somewhere in the powerband for a gain elsewhere.

 

One thing that I don't see mentioned.....you'd have to redesign the entire valvetrain in order to use a lockscrew adjustment. XJ's valves are acted on directly by the cam pressing on the shim (and the bucket pressing on the valve stem). There are no rocker arms or push-rods, as are found in a Chevy 350. There just isn't any extra space in the head for an alternative method of valve adjustment. Yamaha built as compact (and reliable) a valve train as could be made.

EDIT Stu mentioned it.

 

What's the redline on a Chevy 350? How much did it cost to get the redline that high on your "race" 350? What's the redline on that 30+ year old Yamaha? How much did your bike cost? Now add the cost, complication, additional weight, plus your time to your Yamaha....Are your power numbers better? And even in the best case, net net, will you have save any time in adjusting your valves?
In my opinion, it seems like the learning curve is much shorter if you just figure out how to adjust the original setup.

 

well now i understand the design a little better. i see that adjustable lifters are not possible on these engines. i can shim the valves thats not impossible i was just looking for a little more user friendly option. oh well

@patmac6057: the 350 has a 7000 rpm limit, 350 horse, I-beam rods, and some more that i cant say... also has a big block "chevy", merlin III block (cant say the cubes thats a secret), .820 lift cam, scat rotating assy, merlin heads, ratio rockers, 2.25" valves, and much more. its getting scary close to 1000 horse with a 7300 rev limiter and 4000 studder. as for price, my 550 wouldnt buy the block and heads alone.... both engines are in mud racing trucks that i do not own or drive i just hang out and help work on them a little.