Proper Crankshaft Length Measurement

[Mr Mower Man]

I need to replace a failed Honda GX340, and I'm trying to get the right crankshaft dimensions. The 1" diameter is the easy part. It measures about 3-5/8" in length from the oil seal. But there's a mounting face that extends past the oil seal (haven't measured how much). Should I be measuring from this point instead of the seal? This is kinda basic, but I haven't done that many repowers, and the info I've been able to see seems inconclusive.

[bgsengine]

As you may learn in Briggs power portal - best to get one with a crank measurement the same as the length from the crank's "step" to end of crank , then figure your keyway needs, and the center bolt size (if one is used) - If the crank ends up being a little too long you can always cut the end down to the size you need and re-drill/re-tap the crank threads (better to drill and tap threads before making a cut of the crank) We've done that a few times in repower jobs where the "program" (best price) engine had a crank just a bit too long (in one case, had to trim an inch off) as long as done cleanly and according to instruction they'd have no trouble approving warranty if any came up Of course, if you "guess right" and get one with the same length as the one you have , you may wish to note that down for future reference .. but I think it may even depend on engine model and application as to how the crank is measured... But if you measure from the mounting flange to end of crank and the crank ends up being too SHORT, you can't really make it longer, right?

[Mr Mower Man]

Yes, very true. In this case, there's no danger of the crank being too long. I'm worried about it being too short on the Briggs promo engine. But...another option, very easy to do, would be to drill whatever holes in the frame necessary to scoot the new engine toward the PTO end a half inch or so. This particular scenario will allow me that option.

[KE4AVB]

Maybe this help on measuring the Honda GX340 series PTO.

Honda GX340 PTO Dimensions

Kinda looks like there is only 8 options to replace the Q type. plus one that is longer.