Author Topic: do i need new valve guides? (Read 2836 times)

oldk6guy · « **on:** June 24, 2011, 05:01:37 PM »

i bought new valve guides from cycleX assuming i would need them to do a proper rebuild of my head to go with my big bore kit. however, at the time, i did not know that it would cost me $200 to have the guides installed and that a valve job(additional $200) would be necessary with new valve guides. so, here is a pic of the tops of my pistons i would like you all to tell me what you think. i bought the bike in non-running condition, i do not know if it burned oil, i found a broken piston ring on No. 2 that is why it is black. please help, i want to ride this summer!!!

dave500 · « **Reply #1 on:** June 24, 2011, 05:50:41 PM »

have you removed the valves from the head?with the valves out pop of the seal at the top of the guide,then with a very clean valve stem and guide try inserting the valve into its guide so its about half an inch open,then rock it around back and forth,how sloppy is it,make a cardboard rack and number it to keep the valves in order,they must go back into the same place they came from,youll need a valve tool to reassemble the valves,they can be removed without one by placing some rag in the combustion chamber and lay the head flat on your bench,then carefully square a socket over the retaining cap and give the socket a good swift rap,this should dislodge the little wedge shaped keepers that you mustnt loose,then the valve should drop out,the keepers dont have to be kept in order.

wrenchmuch · « **Reply #2 on:** June 24, 2011, 06:53:10 PM »

By asking us to look at the pistons are you asking for advice as to whether or not you should bore it ? We'd need a look at the cylinders in that case . Is there scoring on the cylinder walls ?

oldk6guy · « **Reply #3 on:** June 24, 2011, 07:24:15 PM »

Quote from: k5streetfighter on June 24, 2011, 05:01:37 PM

i bought new valve guides from cycleX assuming i would need them to do a proper rebuild of my head to go with my big bore kit.

as stated, it will be bored, yes the cylinder is scored. broken piston rings tend to do that. i was hoping that you guys could tell from looking at the piston tops if i would need new valve guides or not.

Dave, thanx for reminding me to keep the valves in order, i did so with all of the rocker arms and the rest of the head components but completely spaced about the valves, you saved my life!

Jon · « **Reply #4 on:** June 24, 2011, 07:42:45 PM »

Hi

Can't tell the condition of valve guides from the piston tops.

As Dave said you have to remove the valves & check the play.

Cheers
jon

oldk6guy · « **Reply #5 on:** June 24, 2011, 08:08:27 PM »

how much play am i looking for? non? very little? some?

dave500 · « **Reply #6 on:** June 24, 2011, 11:09:15 PM »

umm?very little play,where the guide protudes into the ports,if the wear is bad(along with the seal)you might see tell tale baked on oil build up around the bottom of the guide in the port,or the back of the valve head looking pretty oily,ive gotten away with murder on some of the old engines ive just sort of taken apart and re assembled as a runner,,then again ive had a few smokers as well,if youve purchased the guides already and your going a rebore,new guides will go nicely,ive had these rebored and never done guides because they have been ok,i know your trying to save a bit of money(not just pocket change),see how they look,approach another engine shop like i said and with your head show them the guide wear(pick their brains),there is a specified wear limit involving dial indicators and such but i dont think you want to go buying specialist tools for a one off job?,,one last tip,,the very tip of the valve stem where the rocker screw activates it(makes contact)can develop a small "invisible" burr,this will prevent the valve coming out easily,dont force or hammer it,,just file it off gently and wipe the stem before you pull it through the guide.

oldk6guy · « **Reply #7 on:** June 24, 2011, 11:53:25 PM »

oops! i did have one valve that had this invisible burr. i persuaded it with the back of my screw driver. there is build-up on the backs of all of the valves. what should i use to clean them so that i can see if there is any play? i have a dial indicator already, i bought it to true my wheels. i can post pics in the morning. thank you so much Dave!

dave500 · « **Reply #8 on:** June 24, 2011, 11:57:45 PM »

oh ok cool,i didnt think you were so "geared up"with a dial indicator,so youve already felt a hard to push through the guide valve?now you know why,just try and see the burr and with a fine file just take it of squarely,youll have to download the 750 manual if you havent already and find the specs for the guide wear,,or someone here might chime in if they have it of the top of their head?found a local engine rebuilder yet or still running with the bike shop?

oldk6guy · « **Reply #9 on:** June 25, 2011, 12:04:10 AM »

i have to use the bike shop for the bore because the local builders cant go that small

i will, however call them tomorrow to see if they can do head work on a MC engine. bike valves and car valves shouldn't vary too much in size. i hope....

dave500 · « **Reply #10 on:** June 25, 2011, 12:12:39 AM »

yeah try and save where you can,i understand some shops cant do the small boring,ive been lucky to get all my bores done at a place that does big stuff aswell,i always say to engine shops and painters to take their time ,im in no rush in the hope of getting a slightly better job?

trueblue · « **Reply #11 on:** June 25, 2011, 12:19:54 AM »

Quote from: k5streetfighter on June 25, 2011, 12:04:10 AM

i have to use the bike shop for the bore because the local builders cant go that small i will, however call them tomorrow to see if they can do head work on a MC engine. bike valves and car valves shouldn't vary too much in size. i hope....

I know the engine shop where I work can only do some motorcycle valves because of the small size of the valve stems, our facing machine can't grip all of them

oldk6guy · « **Reply #12 on:** June 25, 2011, 01:24:36 AM »

how should i clean that build-up off of the valves?

trueblue · « **Reply #13 on:** June 25, 2011, 01:35:06 AM »

Quote from: k5streetfighter on June 25, 2011, 01:24:36 AM

how should i clean that build-up off of the valves?

a wire brush will do it, or a wire buff on a bench grinder

dave500 · « **Reply #14 on:** June 25, 2011, 03:42:16 AM »

yeah a bench grinder with a wire wheel is your best approach,failing that a wire wheel in a hand held drill.

MRieck · « **Reply #15 on:** June 25, 2011, 04:59:42 PM »

I can remove/replace guides and provide a Serdi valve job for less than 400.00. KEEP IN MIND...the valves are shot.....you need new valves too. And seals too.

oldk6guy · « **Reply #16 on:** June 25, 2011, 05:29:25 PM »

do you mean "if" the valves are shot? or, are you telling me that they are, indeed, shot?

dave500 · « **Reply #17 on:** June 25, 2011, 06:47:13 PM »

imagine the cost for a late model four valve head K5?

MRieck · « **Reply #18 on:** June 25, 2011, 08:29:54 PM »

Quote from: k5streetfighter on June 25, 2011, 05:29:25 PM

do you mean "if" the valves are shot? or, are you telling me that they are, indeed, shot?

Yes....they are 35 years old....they are no good. They were marginal to begin with.

oldk6guy · « **Reply #19 on:** June 25, 2011, 08:39:33 PM »

this just gets better and better.

MRieck · « **Reply #20 on:** June 25, 2011, 08:50:15 PM »

I cannot control the past....only the future

oldk6guy · « **Reply #21 on:** June 25, 2011, 08:59:03 PM »

the only new valves im finding are the cycleX superflow valves for $150. do you know if they require head work? will they work with the cycleX guides that i have?

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Author Topic: do i need new valve guides? (Read 2836 times)