cb350: Retorqued head bolts, no compression in either cylinder...

[boomshakalaka]

So, this is the exact opposite effect that I would have expected. I had put on a decent amount of miles and had completely forgot to retorque the head bolts. I finally got around to it, and suddenly the bike won't start. I'm getting spark, carbs are getting gas, but it won't run. I figured tightening the head down may somehow have thrown the timing off, so I readjusted the cam chain tensioner then adjusted the timing, which at static did seem to be a bit off. Still nothing. I ran over to autozone and picked up a compression tester using their loan-a-tool program (can return it within 3 months- I think its 3- for a full refund, even though you've used it.) I'm pretty sure I'm using the compression tester right, but it doesn't hold the reading. Like, I kick the motor over, and I see it jump to 30psi, but that's it, and it goes back down to zero without me pressing the release. Is the gauge messed up?


Even if the gauge is messed up, if the timing is fine, spark is there, and it's getting gas, all it could be is compression, right?

 

[crazypj]

Is it a screw in or push in tester?
Either way, it should have a schrader valve in line to hold compression.
Throttle full open?
Check valve adjustment, sounds like it's 'off'

 

[boomshakalaka]

lol, how embarassing... There was fuel in the tank, but only an inch or so, which I guess is not enough for even the reserve to run off. The plugs smelled like gas, but only barely. I figured that meant it wasn't gas. But the reason the smell was so faint was because it was just vapors... *phew*, I guess I don't have a bent valve or anything!...

This is why I love working on stuff... theres the all too common moments of extreme frustration.. but if you keep working at it, eventually you fix the problem, or discover that there really never was a problem...

:facepalm:

 

[boomshakalaka]

Thanks for the quick response PJ. It is a screw in type. I'm not sure what a schrader valve is, but if I had to guess I would say it does. There is a spring loaded valve that will open when there is forward pressure, but close when there is back pressure (like a tire valve.) Then there is the same type of valve up by the dial, which I'm figuring is the pressure release.


edit: throttle full open? Why would this matter? (not saying it doesn't, but I didn't open the throttle, and I can't figure out why I would.)

 

[Rocan]

open throttle allows you to get a more accurate reading while kicking it over as the carb is open.

standard tire inflation valve is a schrader valve... only other common type in the US is the presta valve found on skinnier road bicycle tires. google them.


lol @ no gas.

 

[boomshakalaka]

Ya, I've got the presta on my fixie, but use the schrader screw on converters since pretty much all air pumps work with those. But I just never knew the verbage. And ya, it was the fuel, but I did check and there was fuel in the tank. I figured it was plenty to feed the carbs on reserve. It did cross my mind that it might not be enough.. but if the problem was more serious I didn't want to push the bike over to the gas station, fill up the tank, then have to drain it or take it off full. So I dismissed the thought out of laziness...

Also, random fun fact: Despite some erroneous google information, cb350 fuel lines are infact NOT 1/4in. I knew they looked big, and they leaked after expanding a tiny bit from being in contact with gas. They work good enough if you get clips on there just right, but the real size is 5.5mm! Sadly 5.5mm fuel line is not super easy to come by.

 

[overdraft]

you know how to tell the difference between presta and schrader valves, right? if your pump is schrader your valve is presta... if your pump is presta, your valve is schrader...

 

[bobjohnson]

5.5mm fuel line can be bought from honda for a reasonable price, like a dollar a foot i believe. Also from garden equipment shops, its used in lawn mowers and stuff. Also most of the clear 1/4" fuel line has the right inside diameter and works properly, its a bit loose but i use tiny hose clamps and have no issues with leaks.

 

[skatetheame]

I just use 3/16 fuel line

 

[crazypj]

I use 3/16 as well, don't need clips then as there isn't any pressure to speak of.
Plus, it's still a bigger 'hole' than the one in fuel tap

 

[boomshakalaka]

Ya, I just picked up some 3/16".. looks more like it... the 1/4" is pretty huge.. I'll swap them out tomorrow.