First engine rebuild

[Dumbquestionguy]

How's it going everyone I'm doing my first engine rebuild. my motor only has about 90 psi and time to freshen it up any tips or tricks some of the pros can give a barn yard mechanic before I jump in. First I should tell you what I'm experiencing bike runs fine rides fine there is build up around the old head gasket and looks to be some oil leaking when I did a compression test #1 had 95 #2 75 #3 95 and cylinder #4 was 95 as well I'm gonna check values tomorrow when I get new feeler gauges but the timing chain was nice and snug thank you in advance

 

[Dumbquestionguy]

Sorry for two of same photo

 

[dirtdigger]

The engine should not run fine with those compression numbers, it really shouldnt run at all on #2 with that low of compression. 95 is really to low to fire so I would doubt they are that low if it runs fine. I would suspect your compression numbers are off from either bad gauge or improper testing procedure. Valve clearances too tight are the number 1 cause of low compression on these engines. The stock spec is too tight and will cause valves to hang open and burn.

 

[Dumbquestionguy]

It must be a bad test it or gauge because I cause I was driving it every day before I check today I did all the steps in order but it is a harbor freight gauge

 

[Dumbquestionguy]

Sorry hands are greasy was hard to type last one

 

[Dumbquestionguy]

OMG I screwed up and bought the worst compression tester ever and almost tore a motor apart because of it well good thing I got the valve cover off I can check the clearance thank you dirt digger you are a cb750 god is there anything I should do also does that head gasket look okay I thought I saw oil but my fork seal started leaking so it could have flew back on the motor

 

[dirtdigger]

I mean it looks like the gasket is leaking a little bit but dont know if I would worry to much unless it is leaking bad. Head gaskets on hondas seem to tend to seep a little bit because no one re torques the head studs. I would stop and wait to see how the valve clearances turn out before jumping too far into worrying about anything else.

 

[kirky]

there is never a dumb question but i might give dumb answers. my answer is if it starts easily enough and runs well i would leave it alone until it gives you starting and running problems, i tested the compression on mine and all were not as they should be after 40,000 km they were down to the low 100's but it starts goes like stink and leaves my mates 1200cc trumpet for dead up to 90mph and ticks over ok, if it aint broke don't look for trouble because if your like me it ends up being a job that didn't really need doing and costing lots of money . i have made this mistake many times over the years and wondered why i never have enough money for the PUB

 

[Dumbquestionguy]

The compression tester I bought is know to give terrible readings I did all this for nothing lol you make a good point I'm a farmer and that's what we always say "if it ain't broke don't fix it"

 

[dirtdigger]

You still 100% need to check and adjust the valves. If you dont they will get tight and you will burn the valves, guaranteed.

 

[Dumbquestionguy]

I checked the valve everything is tight but some are right on where do I find a kit to fix and does anyone have a video of them doing it if possible

 

[brettp]

Lots of good vids on YouTube. You can buy a bunch of various sized valve shims online (forget where, sorry). And I would suggest buying the motionpro valve tool.

 

[dirtdigger]

Keep in mind gap needs to go to .005" do not use honda spec clearance. Honda should still sell shims. hotcams used to sell shim kits dont know if they still do.

 

[Bo82CB]

https://vintagecb750.com/collections/engine/products/valve-shim-kit