GCV160 questions...

Scrubcadet10 said:

Honda GC's aren't like car engines... if you change, advance or retard the cam wheel, it's going to run bad or not at all. the gcv190 carb may fit, but being for a larger engine, may run too rich and pull down performance. going off memory on the GC's i've tore down, the duration and lift is the same. and even if you did change the duration, it will run bad if you don't change the ignition timing, which is virtually impossible... unless you were to get an offset flywheel key which do not exist for that engine.
as far as the lighter blade goes, contact the people you bought it from and ask if they know the maximum RPM, or blade tip speed it can be run at... centrifugal force is very strong, and is also proportionate to the mass of the object.

Click to expand...

Thank you for the response.

I probably need to get it into my head that the little Craftsman mower is not a racecar. Lol. But it is an internal combustion engine, so certain principles remain nearly universal... although some things do not scale in a linear manner.

I, myself, appreciate torque over horsepower... I like the mechanical leverage of a long stroke crankshaft... I generally prefer overhead valve architecture... but, BUT, what I have is the smallest possible displacement, shortest possible stroke, overhead cam GCV160.

I could just get a bigger mower, but I am not going to do that. Since I don't have the raw torque, I have to go for average HP. I know I am going to raise the governor speed, and I really don't want to run out of fuel. Thus, my interest in the GCV190's carb... I don't know if a 13% increase in RPM's justifies installing a carb from an engine with 19% more displacement, but I really don't want to run out of fuel.

It is disappointing that the cam duration and lift is the same between the two, I wonder why they have separate part numbers. Actually, they dont. Huh. I could have sworn my original search(es) shown different part numbers for the GCV160 camshaft pulley and the GCV190 part. They apparently use the same cam wheel. That simplifies things, I suppose.

Good call on needing a new timing pickup on the flywheel if one was to advance/retard the cam. I am probably not going to mess with any of that since there is only one cam profile available. I guess I could still try retard this cam a tooth or two, since I am raising the governor speed... but I'm probably not going to. If the GCV190 cam had more duration, I would have been willing to advance it a tooth or two in an effort to keep torque where I want it. I think it would have been cool to see the difference between a small cam retarded a couple teeth versus a large cam advanced a few teeth. But, oh well.

After doing a little math, a 5% increase in jet size may have actually been a little conservative... I probably should have went up 10%, and ordered the 0680 jet. As it turns out, I would probably need to spin my '160 to about 4K to average the same air/fuel requirements as a '190 at 3500rpms... that would be a ~15% increase in average engine speed.

I am dubious of revving to 4000rpms with an aluminum cylinder, and nothing is forcing me to spin the motor that high. I don't have uber-grass that is exceptionally hard to cut. It's just my morbid curiosity and desire to tinker. Trying to match the air/fuel load of the '190 @ 3500rpms is a completely arbitrary goalpost.

Might actually need that bigger carb, if I do decide to chase 4000rpms. Even if I can put a large enough jet in the '160 carb, I don't want to suck the bowl dry... carbs aren't really my thing, so I don't know if bowls running dry is really a problem... this whole mad scientist experiment is actually an attempt for me to better understand such things.

If I am increasing the main jet size 5-10%, should I also increase the pilot jet size an equal amount? A lesser amount? More than I increase the main jet? Does the pilot jet size even matter that much since it is low throttle operation, and the GCV160 has Auto Choke, and the pilot isn't adjustable anyways. Lol.

Looks like the '160 comes with a 0350 pilot jet... and they offer 0380 and 0400 pilot jets. I am thinking that +5% on the pilot jet, and +10% on the main jet would be a good place to start, but I don't know $#!+...

The Honda/Keihin "constant velocity" carb is an interesting piece to use on a lawn mower, me-thinks.

It [the Constant Velocity Keihin carb] has an emulsion tube, which is something Weber has developed extensively to modify fuel curves... generally to provide mid-range adjustments. A lawn mower has no mid-range to adjust.

And this is not the same CVK casting/body used on dirt bikes, so to carry over that emulsion tube has to be for some economy/emissions gain. My only assumption being that literally any measurable emulsion allows smaller jets to be used, overall. I wonder if Weber emulsion tubes fit... that would be neat.

Has anyone bother re-jetting their push mower carb? Particularly a GCV160/190 carb?

The demand of a 160cc engine @ 3500rpms is similar to that of a 70cc engine @ 8500rpms... and such engines are using #80 main jets, #40 pilots. The GCV160 has a #55 main jet from the factory. The GCV190 has a #65, for reference. Both the GCV main jets seem on the lean side.

I have already ordered the #65 main jet for my GCV160, which still seems to be leaving very little margin of error, all things considered... especially if I plan on turning up said GCV160 to ~3600rpms.

Would a richer main jet, something like a #80, have any sort of cooling effect? Every little bit helps with an air cooled engine (especially one without an oil pump/cooler).

Would there be any benefits to adding Honda's little vacuum powered fuel pump to a lawn mower? The 16700-z0j-003 pump appears to be standard on some other GC160/GC190 models, as well as GX engines.

Although it provides yet another component that could potentially fail, I am relatively confident in the simplicity of the mechanism to last for what I would be asking of it. I could even isolate the pump, itself, from vibration with a creative mount utizing rubber or polymer spacers... if such measures might be remotely necessary. The generators that use them do not seem to go through such efforts to protect the pump from vibrations.

Again, I don't know if there would be any benefits... other than possibly guaranteed fuel supply on ridiculous sidehill runs? Pick a different approach. Lol. And, if the whole mower is that tilted, the pickup location of the tank could be above the level of the fuel in the tank, and no pump is going to solve that.

Would there possibly be any drawbacks associated with installing a vacuum operated fuel pump?

It's not like that vacuum signal ahead of the ventruri/butterfly is being used for anything else... nor will tapping the intake to access that vacuum signal weaken or otherwise affect the function of the carburetor downstream. So, I don't see anything wrong with delivering an ever so slightly more consistent supply of fuel... obviously the vacuum operated pump does not overpower the float/needle, given that this exact pump is mounted on various other models within the same family of engines that I am tinkering with.