Compression and Carbs

[dan1995]

well larry , you "helped" more than i ....at least you drank more beer

[alimey4u2]

That's a moot point Dan......

Joking aside, it was Prestons attention to detail that really impressed me. I can be "anal" at times at perfectionism, but Preston was right there with me.......

Nice Guy too.......

[HondaJohn]

Well, the drinking beer part is very, very important so you probably deserve more of the credit than you realize.

[EMS]

Preston has many talents. Have you ever seen him giving a how-to-deal-with-your-husband's-motorcycle-addiction speeches to ladies?

[Larry Zimmer]

Thought there might be some stuff here to make it worth another look-see.

[HondaJohn]

Well, it has been awhile since I posted my question about compression on my 81 CBX. Since adjusting the valves, doing carbs etc.. etc.. and putting about 300 miles on it, the compession is now between 135-146psi. Adjusting the valves brought them way up. Had two that were too tight so this explained that low compression. I have a 79 with an 80 motor, 16k miles, and it has compression of 131-141psi. I am currently baffled by the ebayer that claims his silver 79 now on ebay, has 175 psi in all 6 cylinders. Has anyone ever had this kind of compression on a stock CBX? 175psi in each?? I am re-learning a lot about these bikes and have collected four of them 79, 80, 81 and 82. The 80 and 81 came from the original owners and are 100% original/stock.

[EMS]

The method on how you check compression and what instrument you use may have a lot to do with the number you end up with. The run-of-the-mill meters may vary quite a bit. The manual spec says 171PSI +/- 14 PSI
But even that is a conversion from the old metric spec of 12 +/- 1 kg/sqcm and does not quite jive , if you use the correct factors. I have two PSI gauges that are off by at least 10% from each other. If you squirt some oil in the cyclinders and check your compression, you may get a higher reading.

[HondaJohn]

You are correct about different methods of checking compression. I check it with all plugs removed, throttle fully open, engine slightly warm (for obvious reasons), air fiter in, air box lid installed, cranking until gauge needle stops/peaks. Regardless of how the compression is checked, I have never heard of or witnessed a compression of 175 psi and this is the original question. I don't care what method you use, I dont "think" you will ever get 175 psi - in all cylinders??? Not happening!! Unless you have a gauge that is stuck on 175psi....

[alimey4u2]

"Just" did a compression test with a warm engine that needs to be blown out a bit...156-165psi were my readings...