[cheapparlortricks]

I just got my new valve springs for my cl350, making moves to replace the valves and all within the next few days. I ordered the valves and guides months ago because I knew the valves were damaged, but I wasn't sure about the state of the valve guides- just bought them cos I thought it'd be a good idea to replace both at the same time. But after reading about valve guide replacement I'm a little nervous about whacking out the old ones without the proper tool, so if I don't have to replace them that'd b cool. If I measure the inner diameter of the old valves and they're to spec, is it worth keeping them in? Is there anything else I can check to see if the old ones are still good? Or is replacing the valve guides not as scary as it seems? I've read a few threads here about valve guide replacement, but is there a best way to do it (without the valve guide remover/installed tool mentioned in the manual)?

 

[Lefty]

I check them for size with a starret small hole gauge in conjunction with a micrometer. The best way to remove and install is to heat up the head and use a threaded puller. Some times best to push into the chamber if you can. Any carbon stuck to the guide will score the bore and its hard to tell if it's all off. If you're lucky the new guides will be close to concentricity with the old and you won't have to cut the seats too much to seat the valves. If not you have new problems. Then they'll probably have to be reamed or honed, and as we are dealing with .001" one way or the other making or breaking the job.... Well I wouldn't trust just anyone, which is why I'm trying to learn it myself. Easy to make it work, but a good chance at being worse off than it was. I'd confirm it needs it before getting out the hammer.

 

[Boomer343]

Well it's scary if you screw it up!

The driver tool can be made if you have the equipment but it isn't as simple as driving them out then another one back in. After the guide is properly in place the guide needs to be reamed to size with the proper reamer. This is a lot more delicate work and it is easy to take excess material.

If you take a new valve and without lubrication slide it into an intake guide until you are still able to hold it with your fingers on the valve face and the stem. Now gently rock the valve side to side, delicately, this is a feel measurement. Ok have an idea of the amount of movement repeat on the other intake guide. Go back to the first then back to the second. Same feel or different.... now go to an exhaust guide ... there will be more movement compared to the intake side but it should be slight. Do the second guide, compare. Repeat.

Now package it up and send it to Tools ....

 

[cheapparlortricks]

Thanks for the tip Lefty. If I have to replace the guides, I'll do it that way. I need to get a dial gauge- when I was last working on this bike in the fall I'd just borrow one from the machine shop where I worked, but have since left that job. I only have a micrometer, mitutoyo calipers, feeler gauges and other general measuring devices here, and even though the calipers are pretty dead on, using it to measure the ID of the valves with it seems like an inaccurate way to measure.

Boomer, I tried wiggling the valves. It feels the same with the old valves and new. What does this feel test tell me though? Is it checking the wear of the valve shafts?
Another thing that might be important to mention: if I put my gloved finger over the top of the valve guide and slide a valve in or put, there's a seal/suction that pulls or pushes the nitrile. The air escapes somewhere, but there's still a vacuum. Is that a sign of anything?

Would it hurt to put the new valves in, lap them, and test to see if the seal is proper by pouring gas or acetone in the head overnight to see if it leaks?

 

[cheapparlortricks]

A guy I know that has a motorcycle shop in my area said I should just try lapping the new valves without replacing the valve guides and checking for leaks- I don't know to what extent I trust his knowledge/ I don't think he's done much valve work, so I'm hoping one of yall has some insight. If I put in the new valves and it doesn't work, am I irrevocably screwed/would I have to buy new valves (again)?

 

[ancientdad]

Even if the guides were worn, lapped in valves reassembled might not leak in an acetone test - but would still be sloppy and inaccurate when the engine was running due to the excess movement of the valve in the guide while in motion. I've been fortunate to have never had to have a guide replaced, but the older these things get, the more wear on all the parts on a good used head. Measure, decide, and if it's out of spec, send the head to Tools as mentioned above. You don't want to attempt doing a valve guide with no experience, and trusting a local shop that you probably have no knowledge of their expertise in that area on a motorcycle engine wouldn't be the best plan IMHO. I had my cylinders bored and the valve seats lightly cut by a long-standing local speed shop who I've known for decades, but they do that kind of work all day long on all types of engines... valve guides on a bike head, not so much and maybe never. As far as your new valves are concerned, as long as you didn't run it very long you'd be able to re-use the valves - just so there was no excess wear on the stems from the sloppy guides

 

[Flycast47]

I agree with a'dad. The most common issue with worn valves is the seating area develops a curved profile as does the corresponding area on the valve seat. The designed interface is straight profile. Just lapping the valves and seats won't remove this radius. Also getting a good 3-angle valve grind will improve sealing and flow through the combustion chamber.