yet another valve adjustment question

mike12374

mike12374

builder never finished
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Hey everyone. First of all let me say this a very helpful and useful forum. This topic may have been covered so if it has call me a dumbass and point me I the right direction. My question is aimed at the brains on this site houghhandmade, drewpy, ext. So I hope you guys can help.

I was doing a valve adjustment on my 81 xs400sh yesterday and I ran into something strange. When I would adjust my valves on the left side(compression stroke) the valves on the left hand side would become loose as they should but I noticed the exhaust valve on the right side was loose as well. Now keep In mind that the right side intake valve was tight. When I went to do the right side , tdc compression stroke, the right side valves became loose but the left hand cylinders intake valve would become loose. My question is is that normal? If not what could cause this? Thanks in advance for the help. Just a tidbit extra did a compression test and I got 120 left and 150 right with no noticeable run off of pressure.
 
When doing valves only worry about the side you are adjusting. The other is in a different cycle at this time so it will not be the same. Just remember not the let the fly wheel spin back when you hit tdc for each side or the adjustment will be off. It puts slack in the cam chain which you don't want:wink2: 120-150 is a big difference between the two. Are you doing the test with the throttle open all the way while you spin the motor over? That is how you do it. I would check valves again. If that don't help I would put a oz. or two of oil in the low psi cylinder and see if it goes up. If it does it's rings:(
 
When I do the compression test I do 5-7 kicks with the throttle completely open it seems like the low side takes longer to build compression then the good side. I've got it to 150 on each side but it takes far more kicks to get the low cylinder up to 150. Thanks for your reply I will double check the compression and post results later. Thanks for the sppedy reply xs Chris.
 
15,000:/ but it doesn't smoke and besides running a little lean on one side and perfect on the other with a dead spot from 5000-7000 rpm it runs great. I have pods and straights with baffles. I decided to check the valves because it was a little chattery and necessary to tune up the carbs properly as you know. I still plan to reclean and sync the carbs with a nanometer if it ever decides to show up to my house.
 
:thumbsup: A 5-7k dead spot would be you needle jet or needle position. I would first make sure the needle jets holes are all clean. And if they are you may need to shim the needles a bit to raise it up to make them richer.
 
I have them shimmed with 2 spacers unfortunately I don't have clipped needles I'm at 45 pilot 145 main 2 up o the needle and 4 turns out on air screws. I ordered 147.5 mains do you thi k that might solve the problem? Would you reco.end bringing the needle back down to stock?
 
And xschris take a loom at my album with pics of my build looking for feed back positive or negative thanks
 
Have you synced the carbs with a manometer? You may be too rich in the mids if you have two shims and it is still there. Your main jets are for only 7-9k rpms. So if it pulls well there I would leave them.
 
Manometer just arrived today Wil sync them tomorrow morning and report back also I noticed that the cheap ass pods I bought were blocking 75% of my air ports in the face of my carb. What conditions produce/ how would that effect the bikes performance. Finally forked over the cash for some uni pods that aren't tapered inside thus freeing the holes up. Should have just done that in the first place
 
So synced carbs oiled filters set valves and the bike is running like a raped ape ! Smooth throttle no hesitations or dead spots on wot just great. I have become obsessed with engine temps trying to figure out what is too hot . It's about 70 deg here in Ohio and after a 30 min run ( mostly backroad speeds with no traffic 35-50 mph average wot to get up to speed) I got back to the gerage and shot some temps with my ir thermometer. I got 320 at the head fins closest to the plug 280 at the front of the rocker cover and around 240 at the case right above the clutch cover. Soooooo my question is that too hot? What is normal temp for these bikes? Should I be worried about these readings? If they are too hot how do I bring them back down?

Also my engine has been painted with high temp paint. Can that effect heat dissapation/ cooling?

Any help would be greatly appreciated:wink2:
 
Paint can affect temps. I would try to limit your WOT as much as you can. If your racing the bike and are willing to rebuild it every few years then that's up to you:wink2: Shifting at 5-6k will be a LOT less stress on parts:) 320* at the head by the plugs is hot. Both my bikes run between 265-285* even on 85* days. The lack of mufflers, or the way you drive it may be contributing to those temps. What do your plugs look like?
 
Haven't checked plan on doing a plug chop tomorrow and see what happens. You mentioned the lack of mufflers contributing to heat. If I packed my tips with stealwool around the baffles would that possiably help? I was thinking of doing this anyways to cut down on the noise. Is it the back pressure that helps dissipate heat? I know that many people believe that "back pressure " is a made up term. And that the excessive exhaust decibels from a free flowing exhaust is enough to create the desired "back pressure "but I'm not sold on that theory. Any thoughts?
 
mike12374 said:
Haven't checked plan on doing a plug chop tomorrow and see what happens. You mentioned the lack of mufflers contributing to heat. If I packed my tips with stealwool around the baffles would that possiably help? I was thinking of doing this anyways to cut down on the noise. Is it the back pressure that helps dissipate heat? I know that many people believe that "back pressure " is a made up term. And that the excessive exhaust decibels from a free flowing exhaust is enough to create the desired "back pressure "but I'm not sold on that theory. Any thoughts?
Click to expand...

Any bike/motor with a good set of mufflers will tune better than a straight pipe. With no back pressure the exhaust gasses move faster out of the motor making the combustion chamber burn hotter. Think of it as a wood stove chimney. The better draw you get the hotter the fire. Back pressure in a 4-stroke motor also has effects on the valves and how they operate.
 

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