Measuring the gxv120 Cylinder Bore

After I got the gxv120 cylinder honed I began to have doubts that the cylinder was still within spec. After all, this engine is pushing 30 years old (!), and was running super high revolutions when the tear-down began. So I decided to do some rough measurements with a telescopic bore gauge and calipers that I borrowed from a friend. Luckily the hr214 shop manual had the specs for the bore, and after taking some measurements it looks like my bore has about .05mm of wear, but is still well within spec. If anybody wants to do a tear down on one of these hondas and take the measurements, you need to take your time and do multiple measurements. I followed the directions from the video below:

Tools used in video:

Telescoping Bore Gauge Set

Digital Caliper

Dial Bore Gauge

Like Jaf says in the video, the dial bore gauge is the best solution if you're building a serious engine, but for a lawnmower engine that is measuring so far below tolerance with the telescoping bore gauge set, I think I'm fine. I ordered some parts from boats.net too...hopefully next week the rebuild will start.

Honda HR214 Manuals, HR194 Manuals, GXV-120 Manuals

So while the machine shop is doing unspeakable things to the honda gxv120, I'm getting my stuff in order so I can start putting the pieces back together when I get the block back.

Honda GXV120 Service manual-This is the service manual for the hr214's engine-in three languages no less!

Honda HR194/HR214 Service Manual Online- CB left us this link in the comments, its the service manual online, for FREE! SWEET!

Honda HR214 Parts diagrams-Actually a link to Planopower, they appear to have a pretty complete list for the hr214

Honda GX Carb cleaning video-How cool is this? Bwdbrn1 posted this on the "my tractor forum"; its a 8 minute video showing how to take apart and clean a honda gxv120 carb!

Honda HR214 Manual-Just a link to e-bay for now; I haven't been able to find the pdfs of the hr214 online yet, but I'll keep looking.

Honda HR214 Owner's Manual-Probably not gonna use this one for a while, least not till this beast is back together!

Honda gxv120 and gxv160 Carb Services checklist-Really nice diagram of what to check for when something is amiss with the Keihin B0E3A carb

Honda hr214 lawn mower engine tear-down

And so it begins! I spent the majority of sunday tearing the gxv120 down. I used the official honda manual for the disassembly, but didn't necessarily go in the order prescribed.

Tools: No special tools required, just a wheel puller and a strap wrench to remove the flywheel. Beyond that, I have a motley assortment of metric wrenches and sockets. I would need some special measuring tools if i was going to check out engine internals myself, but for now we're OK since I'll be sending the block out for honing before I drop the new rings in. Oh, and a digital camera to take pictures as you go, and some baggies to store the parts.

Manuals: Just some youtube videos and the official honda hr214 manual. I'll use the parts manual from planopower.net or boats.net to order the stuff, but it wasn't necessary for the take apart.

Steps: I should have removed roto-stop assembly from the bottom of the mower, then taken the engine off the deck. Instead I left the mower on the deck, too it apart until I was down to the block, and then removed the roto-stop assembly. My back is killing me from all the bending over, even though the mower was on saw-horses.

So what does the inside of this small engine look like? Really, not fantastic. No metal shavings, but the bore is as smooth as glass, no cross-hatching in site. Ergo, definitely a hone job before it gets put back together. I'll also have the machine shop check the bore to make sure I don't need an over-size on the piston/ring set, but I would guess I'm ok there.

3800 rpm Honda gxv120!

So after posting my "before" tear-down  video of the smokey hr214 mower, some of the guys over at "My Tractor Forum" said that Yoshimi was running a bit fast...like a thousand rpm fast! Whoops. So I ran out to Northern Tool and picked up a digital tachometer like this one and hooked it up. After a little  learning curve, this tach was pretty easy to set up; red wire gets wrapped around the spark plug lead, and the white lead gets grounded to the frame. The hr214 sparks every revolution (even during the exhaust stroke), so i left the stock settings in place, but you can also set it for different types of motors (distributor vs. non, etc).

So what did I find? Holy crap, this thing was about to fly apart! The specs for the gxv120 call for about 2,000rpm at idle with the blade disengaged, and I was up around 3200 at idle, and around 3700 at top speed.

Hmmm...after reading the manual, it looks like the idle gets adjusted at the carburetor via the throttle stop screw, but no dice! Long story short...the breather hose was actually broken off a the block  and had pressed the governor arm as far as it would go-keeping the engine running at top speed. After seeing the breather hose venting to the outside world, I decided to go straight to the tear-down, and spent most of today taking the gxv120 apart. Video of my rev-happy Honda below: