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crf valve train

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Don't tell me that we have to model the head at work next week to calculate the thermal expansion of the exhaust valves vs. the head. That's ok though, the guys have been dying to redesign the head with an integrated supercharger. This is what happens when 4 guys that ride bikes have Solidworks and CNC mills at their disposal. And people think were are designing medical devices. :):D :D

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you guys do know that metal exspands in more than one direction. I am talking about all engines and all componets of an engine exspand. You didnt anwser my question . If the valve clearance increases as the engine gets hotter, why does the engines valve noise quiet down as it warms up. Another example , metals in all diresctions. If you build a high rpm drag engine with really tight piston, it will idle fine and run fine . But by the time you hit second gear wot the engine will lock it self down. Because as an engine warms up the clreances decrease. Thats is why they (honda) want you to have the clearances because everything tightens up as it get hotter. Another example on honda car engines I have had cars come in running bad when they warm up , because some jackleg(person who does know what their doing) adjusted the valve way to tight. You want to know why because as the engine got hotter metals exspand , in all directions , and the valves did have the proper clearance and when the engine got hot the valves hung open slightly.

Heres quote straight from one of my school books

"Solid lifthers(non hydraulic)do not have this built in feature and require a clrearance between the parts of the valve train. This clearance allows for exspansion of the components as the engine gets hot. Periodic adjustment of this clearance must be made . Excessive clearance might cause a clicking noise. This clicking noise is also an indication of the hammering of valve train parts against one another."

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explain why the crf is out there running fine you just came in from a long ride and let it cool off and you cant get it started when you go to check the lash there is none infact the valves are slightly open.tight lash on a multi cylinder engine with a common intake manifold can exibit low manifold vacum and cause poor performance @ low engine speeds.early engines probally did require lots of lash but i think it was more to do with poor ability to grind cam shafts and there had to be more clearance for bad base circle run out.if you need an example of valve adjustment from a manual look @ the old harley iron sportster you would set the push rods adjustments so you could just roll them when the engine is cold. and as they get hot they gained clearance.also all of my engineering books say that the exsesive noise coming from the valve train when it is run loose is not the lifter smacking the lobe but the valve impacting the seat because its to close to the end of the closing ramp .we had the same problem with hydralic HD cams with real fast ramps they made to much noise for the customers bikes so we just kept slowing the ramps a little when regrinding the cams until the engine was quiet.

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Lowside21, I don't have the energy to tell you in great detail tonight why you are wrong. Perhaps tomorrow.

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Ok,ok, I got one.

If you look in a mirror and right and left are reversed then why aren't top and bottom reversed??? :D :D RR.

Mommy my brain hurts. :)

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lowside21, your textbook is referring to an old pushrod engine. When the lifter and pushrod expand, the clearance between whe rocker and the valve becomes tighter and the expansion of the old vintage iron head is not enough to make up for it. Now put the cam up on top of the valve and toss the lifter and pushrod in the trash and throw in an aluminum head and you have a whole different scenario because aluminum expands much more than iron or steel. That is why a tight aluminum piston in an iron block will seize and your valve clearance will still be within spec. because they are completely unrelated.

Now ride_red's head is beginning to hurt so adjust your valves according to the manual and ride dude. :)

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Dirty thumper , I agrea with, do what honda tells you. They know more than any of us can guess. I should have said that from the begin with. That is mainly what I had in the back of my mind all along when I replied. I am only an automotive technican, GM factory trained and certified and More recently switched to Honda. I have been trained by Honda aswell. I havent done any scientific researce, or any cobble'd together garage exspiriments . I just listen to what the engineers from companies like GM and Honda tell me. I would say just go by the manual. I stand by what I have said . That is the way that makes the most sense, and is the way it has allways been exsplained to me in school, text book, and from my drag racing exsperience. But I am going to researce this and let you know if I just misunderstood. I am going to call the engineers at the honda southeast training center to find out for sure.

Also Dirtythumper about the old push rod engines . The 331ci in my mustang has alluminum heads as well, so have most pushrod engines since the mid 80's. the difference is the they have hydraulic lifters(or tappets). Over head cam engines with alluminum heads have them to(the Quad four and norstar v8 come to mind). Hydraulic compesates for the exspanion caused by engine temperatures and for normal engine wear. Fords "mod" v8's have ohc with a cam follower(rocker arm) and hydraulic lash adjusters. Basically engine oil pressure keeps the cam lobe,rocker arm and valve stem in constantant contact, in other words it takes up the slack while the engine is cold. That is why engines with hydraulic tappets , cam followers , or lifters have significantly less valve noise when cold. Thats why I was surprised how noisy a little civic is when cold started , they are nonhydrualic. They quiet down when they warm up , unless they need adjusted. In which case they are even noisier when started cold. Ohh well I am not trying to be hard head . I know my tone come across wrong over a computer. Iam not very good at comunicating threw these things. I just have 7 years of day in and day out 10-12 hours a day working with engines and thinking about engines nearly twice as much since I was 13.

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I just had a totle Failure of a Kibble and White intake valve. It destroyed my engine. One intake valve head broke off in the cylinder destroying 2 exhaust valves bending them.

Destroyed my head and cylinder one intake valve is still good, not bent or damaged. found the piston at a 45deg angle in the bore due to the pounding of the intake valve.

valve destroyed the head cylinder piston major ouch. did port job on head all that work is gone. Bike ran for about 30 min till boom was just getting the jetting spot on. By the damage seeing that 1 intake valve was not touched I was not over reving the bike at the time and the cam timing was still correct the only possible cause was the intake valve failure. Is ne1 else have this happen to them?

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lowside21, you may find this interesting. Looked up the specs for a particular motor. It is all aluminum (block and heads) overhead cam and no hydraulics. This V6 motor is found in Renault, Volvo, Peugeot and Delorian. The valve clearances are as follows; intake cold .004-.006 hot .006-.008. Exhaust cold .010-.012 hot .012-.014. These valves clearly run looser when hot. :D This is fact and not debatable. I suspect that any motor of similar disign will do the same thing. My earlier comments about pushrod engines were referring to solid lifter motors only. For this discussion hydraulics do not apply. While some pushrod engines may tighten up when hot, some do not change at all. Volvo B30 cast iron inline 6, clearance is .016-.018 hot or cold and these specs are from the factory manual for dealers. I'm not trying to be a hard head either, just saw an interesting topic and had to jump in. I find these forums to be very educational :)

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WaveRider, This happened to another TT'er (extreme165) a while back. He posted a lot of information regarding the failure on this site, but it was a long time ago and I couldn't find the post(s) when I did a search. I know Mike Perry of Kibblewhite got involved as well. Sorry about your bike! I hope you can get it sorted out without too much pain....

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waverunner send the parts back to kibble white so they can inspect the breaks i have had heads pop off from valves before from different manufactures .im going to stir things up again oil pressure does not hold a hydrulic lifter up a gainst 100 to 200 #s of spring pressure plus even higher pressures do to the cam profile it feeds the lifter and is trapped by a check valve . the same is true on crank bearing$ 40 #s of oil pressure can not with stand 2000 #s of cylinder pressure the oil pump feeds the oil to the crank shaft through a hole that is place @ a lower pressure angle and the rotation of the crank forms a high pressure wedge of oil capable of withstanding the cylinder pressure . also engineers from honda gm ,ford chrsler seek information from individuals that are not engineers or @ least not certified engineers.

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Dirtythumper maybe we are getting somewhere? Maybe different engines have different dynamics?The main question in my mind that nobody can seem to respomd to is, "Loose valves are noisy and you tighten them up the noise goes a way or is reduced, When an engine is cold it will have valve noise why does it go away as it heats up?"

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Will a valve with a bigger clearance not open less and therefore have a slower closing velocity, or is it the fact that a valve with a smaller clearance will leave the closing ramp later and therfore have a slower closing velocity?

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with more cleaerance the bucket or lifter is following a faster section of the cam lobe when the valve is seating causing it to bounce.

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with more cleaerance the bucket or lifter is following a faster section of the cam lobe when the valve is seating causing it to bounce.

this is what I was thinking before...with more clearance your pulling the valve away from the closing ramp of the cam.....

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