GX140 Rod Length

[areams]

Anyone know the factory rod length for a GX140?

If not, Has anyone ever used the billet rods for a GX160 in their GX140 without any troubles? (Piston kissing the valves?) Would I use a stock length billet rod marked for the GX160 or is there a different size needed?

I know most of the parts are interchangeable between the 140 and 160, but nothing is ever marked as working with the GX140. Only the GX160 and GX200. I assume the gasket kits are identical.

Getting ready to start my mini bike build. Thanks in advance for the helpful answers!

 

[itsid]

If I'm not mistaking the gx140 shares some dimensions with the gx120 rather than the gx160..

and with that, the con rods might not fit anyways
IF it's the gx120 compatible conrod
the piston bore is 13 instead of 18mm and the crank bore is 26 instead of 30mm

*shrugs*,
on the other hand the gx140 shares the stroke (45mm) with the gx160 and the gx120 shares the stroke (42mm) with the gx110...
so one could assume similar con rod lengths for the gx110 and 120 as well as for the gx140 and 160...
just because that'd help reduce tooling costs for honda

I have no idea..
I wouldn't buy anything w/o gx140 specified as a target
not without measuring the original part first.. (length, bore dimensions, and width of both ends)
if bad comes to worse they changed a few specs over time and the parts don't fit although they should.

'sid

 

[areams]

I am going to be taking it apart in the next month sometime anyway I was just hoping to have parts here first, oh well. I have seen the stroke was close between the two just couldn't find con rod dimensions.

What would the proper way to measure the con rod length be?

 

[bob58o]

I have no idea either.

This says the rod fits gx140, gx160, and gx200.
https://www.lsengineers.co.uk/honda-gx140-gx160-con-rod-non-genuine.html

I'd call ARC Racing and see if they can give you any info. They are the connecting rod people.

Since the 140 and 160 have the same stroke, it might make sense they use the same rod. ARC should be able to give you some better info tho.

 

[65ShelbyClone]

Rods are interchangeable between the GX140, 160, and 200. Same length, same journal, same pin, and same widths.

Also be aware that the flywheel taper is smaller with the 140 so billet flywheels for the 160/200 won't fit. It might be straightforward to swap in a 160 crank though.

 

[areams]

Just read somewhere today about that issue with the taper being different. Thanks for confirmation about the rod length though!! First time I’ve seen someone sure of it.

Should I have a problem using a gx160 head gasket? Haven’t been able to find the thin gasket for the 140. I know bores are different but will there be an issue?

 

[65ShelbyClone]

My 140 came with a head gasket where the bore is already big enough to fit a 160/200. I think Honda just used the same one for all of them.

 

[areams]

I’m going to go for it. Ordered everything I need to get this little small block to rev to 6500 if I ever wanted to take it that high.

Billet rod
22 lb springs
CL2 cam w/ lifters
8* timing key
Gasket kit with the .010 head gasket
Reinforced rocker arms
Header pipe
Open air filter
Lower profile fan

Anything I should be particularly aware or cautious of or something I have over looked?

Going with a torque converter/10 tooth to a 54 tooth rear sprocket. Will be a ground up build with the frame being built around the wheels/tires and motor. Should be a fun little trail rig that can move down the country road when needed.

 

[landuse]

Sounds good to me

 

[areams]

What should ideal ring gap be as well as bearing clearance for the con rod? Plan to plasti-gauge it during reassembly. I have factory specs for valve clearance but for a higher hp engine what should that be?

 

[65ShelbyClone]

Valve clearance can usually it can be set rather tight. The engine expands as it comes up to temp and valve lash tends to open up. The cam card ought to mention a number though.

Ring end gap rules-of-thumb can be found on the net. I don't recall what it tends to be, but I want to say 0.010" per inch of bore size. Too much is better than too little. Too much and there might be slightly more oil consumption blowby. Too tight and it could score the cylinder or pull the piston apart.

Rod oil clearance I'm not sure about. 0.0015-0.0025" perhaps? That's usually what performance street engines run in cars, but they also have much larger journals and pressurized oiling.

Another note: a 14cc "GX200" head will keep the compression up and provide larger ports and valves.

 

[areams]

Great info, Shelby! I've built a few different street car engines but nothing this small so I just wanted to cover my bases for specs if they were different. Info is great!

Only thing I have left to find is piston rings. I think I have found a set on ebay but I was wondering if anyone has any idea if any of the other performance parts suppliers mentioned on here have them? I contacted NR Racing but I haven't heard back yet. Any ideas?


Also, has anyone ever used one of these?
https://www.gopowersports.com/tillotson-tct-mechanical-fuel-injection-carburetor-replacement/

Without knowing much about it other than the description, seems like a much better option than a standard carb purely for tuning purposes? Why wouldn't everyone use one?

 

[bob58o]

Not sure about performance part dealers, but there are plenty of places that sell Honda Parts.

Here are some rings.
https://www.mfgsupply.com/23-11286.html

JacksSmallEngines.com usually have a bunch of goodies too.

 

[65ShelbyClone]

Great info, Shelby! I've built a few different street car engines but nothing this small so I just wanted to cover my bases for specs if they were different. Info is great!

Only thing I have left to find is piston rings. I think I have found a set on ebay but I was wondering if anyone has any idea if any of the other performance parts suppliers mentioned on here have them? I contacted NR Racing but I haven't heard back yet. Any ideas?

Your best bet for finding rings is going to be stockers from a power equipment parts dealer.

You might be able to cross-reference substitute rings based on the ring thickness and bore diameter. 64mm is pretty common in smaller metric engines.

Also, has anyone ever used one of these?
https://www.gopowersports.com/tillotson-tct-mechanical-fuel-injection-carburetor-replacement/

Without knowing much about it other than the description, seems like a much better option than a standard carb purely for tuning purposes? Why wouldn't everyone use one?

The throat on those TCTs is tiny. Frankly, I wouldn't use one just based on their hokey marketing. It's not fuel injection by any stretch; it's a carburetor that uses a metering method vaguely similar to ancient mechanical fuel injection. It's also marketed primarily toward stock utility engine applications.

My suggestion would be to get a conventional slide carb in the 20-24mm range.

 

[areams]

Seemed too good to be true. Neat concept though if ever developed further. For now I am going to go with a new in box spare carb I’ve got laying around for a 208 power horse engine. Eventually the slide carb is going to happen.

 

[areams]

In case anyone has any question in the future, the ARC rod stock length for the gx160 and gx200 are the same one used for the gx140. Mine is apart and I have been working on porting the Head currently. Factory rod and arc rod measured out to be the same.