2019 - Ultimate Yard Kart

[Hellion]

I was trying to goad you into doing some side research to see if you could figure out the mystery but I missed a thread or two and you already covered the special Cobalite exhaust valve and rotator spring earlier.

Good show.

Can't keep up with your different threads. Get organized, man!

 

[JTSpeedDemon]

^^
Ok then, here's most of the threads I posted asking questions about this engine:
http://www.diygokarts.com/vb/showthread.php?t=42098
http://www.diygokarts.com/vb/showthread.php?t=42078
http://www.diygokarts.com/vb/showthread.php?t=42340
http://www.diygokarts.com/vb/showthread.php?t=42362
http://www.diygokarts.com/vb/showthread.php?t=41305
http://www.diygokarts.com/vb/showthread.php?t=40999

These threads also cover my findings about the rare parts on this engine, as well as my reasoning behind some of the mods I plan to do.

 

[JTSpeedDemon]

I aligned the oil control ring wrong. I's the 3 piece kind, and my mind slipped when I was aligning them, so the end gaps of the oil control rings are all aligned.
Soooo, now I need to open it up again, pop out the piston, realign the rings, and put it back together.
That'll be on my "get it done sometime" list, I wanna ride it to see how much less finicky the carb is.

 

[JTSpeedDemon]

Since I had almost nothing to do today, I opened up the HiPo to reorient the oil control rings.
They were indeed misoriented from last time, and the compression ring orientation was less than optimal.
You can see in the first pic the oil puddle I found on top of the piston.
I think the smoking was down to the ring orientation compounding the worn cylinder.
Oil looked pretty decent, a little blackish tinge to it, but still mostly yellow.
Cylinder wall looked about the same as last time, still kind of scratched up. Head gasket was toast when I opened it up, the oil ruined it. Connecting rod journal is in nice condition.

Also, in the Clymer manual for Briggs flatheads, it says that a worn oil control ring will have flat contact faces. That is the case with this engine, so it's also just worn out.

So to sum up the wear this engine has:
Mildly scratched, glazed cylinder
Scratched piston
Worn oil control rings
And I still need to check the valve guides.

Not optimal.
So someday in the future, I need to have the engine bored out 0.01", honed, and install 0.01" oversize piston and rings. The boring/honing will be a job for a professional machine shop for sure.

So if what I did today doesn't help the small oil burning problem, I'm just going to have to deal with it.
But I think it should cure the smoking, since it didn't smoke before I did the rod upgrade. I may or may not have scratched the cylinder a bit during that upgrade.......

Also, I found out that this engine does indeed have the lobe compression release, so I need to pull the cam in the future to remove that.
And to do that....... I have to pull the crankshaft........ and to do that, I have to remove the flywheel, which is stuck........
Yada yada yada, so on and so forth.

Also I noticed today that the front wheel bearings are totally shot, so the front right tire is balding prematurely. Those bearings are ~40 years old! It's no wonder!

 

[J.S.@SMS]

If it's an aluminum bore, a machine shop is a good idea. But if it's an iron bore you can probable hone it yourself (ikd about steel bores). All you need is a good crosshatch to seat tte new rings. When I rebuilt the 196 on my Baja Warrior, all I did was clean the burnt oil off everything (she was a big time fogger), hone the cylinder, install new rings, and replace the gaskets. No more smoke or crankcase oil leak, and it has more power than ever. And that isn't that bad, my head looked like this after cleaning it up.


(I tried to post a video of it running after the rebuilt, but this side won't accept a .MOV file, and I can't change the format on my computer.)

 

[JTSpeedDemon]

It's technically a cast iron bore, but I just call it steel.
As for why it would be best to bore it, that's because it's a bit scratched up, and honing is not a good idea for trying to get out scratches. Too much chance of making the cylinder out of round before the scratches are gone. Honing is to "dress it up" for ring seating.
Also, getting it rebored will help minimize the "taper" in the bore from the piston travel area, where it wears down the cylinder.
Plus, there are oversize piston and ring sets available.

Aluminum bore flatheads are actually not supposed to be bored, there's no oversize pistons and rings, and the oversize pistons and rings for a steel bore will not work in a Kool bore, since they're tin plated vs. the chrome plated ones for Kool bores.
For now I'm just going to put it back together and hope it's fixed.

 

[JTSpeedDemon]

Oh yeah, I checked, and this thing has magnetic oil filler plugs from the factory! Yay!

---------- Post added at 05:53 PM ---------- Previous post was at 05:47 PM ----------

Part number 691663.......

 

[Budget GoKart]

Oh yeah, I checked, and this thing has magnetic oil filler plugs from the factory! Yay!

---------- Post added at 05:53 PM ---------- Previous post was at 05:47 PM ----------

Part number 691663.......

My 8hp has them too

 

[JTSpeedDemon]

Better........

Head gasket came in a few days ago, but I was busy planning our church youth group's White Elephant(great success).
But I didn't have much to do today, I didn't go out and earn money since I'm staying home to rest since I'm still technically sick.
So I went ahead and put it back together(that head gasket is shiny), and while I was at it, I got dedicated pics of the markings on the tin plated piston and the Cobalite exhaust valve for future reference.
The sidecover gasket was mildly torn around the bolt holes, so I added some silicone and called it good, I don't want to wait for another gasket.
I checked the valve guides, and they're fine, should get lots more life out of them.
The piston rocks slightly in the cylinder, so I know for sure the cylinder's worn.
Filled it up with the old, still Ok oil, plus the rest of the fresh oil, and fired it up!

It blew some black/maybe bluish smoke and some deposits onto my hand out of the exhaust pipe, a little more so when I revved it. I let it run and kept momentarily spiking the revs and playing with the tuning.
After a little bit, the smoking went down quite a bit, so I think the rings needed to seat a bit, plus everything needed to warm up.
The smoke at first was probably residual oil, there was a considerable amount when I opened it up.
Afterward I pulled the plug, checked it, and looked into the combustion chamber with a light. Looks like it burned some more oil.


So all in all, it's much better than it was before, it doesn't blow white smoke any more, just some black smoke.
I fixed the ring orientation, and checked things over in general.
It's not perfect, but it's all I can do at the moment. In the future I plan to get it bored out 0.01", honed, and install corresponding oversized rings and a piston. But that's in the future, for now it's running strong.

I just need to replace the trashed front right wheel bearings before I ride it again, I don't want to risk those failing!

 

[gegcorp2012]

What (?) no smoothing out those stepped eyebrows around the valves for better flow ?

I think KartFab has a good video on eyebrow porting for flat heads.

I have Briggs engines on my powerwasher and cement mixer and now that I am getting my hands dirty on small engines, I would consider doing some light head work on my flatheads the next time I have the head off.

Sent from my SM-J700T using Tapatalk

 

[JTSpeedDemon]

If I had a Dremel I would've while I had the piston out, but oh well. It's not too hard to pull the cylinder head on these.
This engine already has a LOT of power, but yes, eyebrow shaving and probably some port cleanup are still in order, and the exhaust port threads will be coming out, since I prefer flange mounting anyways.

 

[JTSpeedDemon]

Ok yeah, I just test fired it, and the smoke is cured, except for some slight black smoke when I rev it. Much better than before.

 

[J.S.@SMS]

The black smoke is from it being rich, so you may want to adjust the high speed a bit leaner, if you can.

 

[JTSpeedDemon]

No, I think it's actually bluish, but it's so faint it's hard to tell.
I know I can rule out a rich mixture, since I have already leaned it out as much as possible and then richened it slightly until it runs well. It's either a small amount of oil still leaking in, or old deposits burning off.

 

[J.S.@SMS]

It's probably deposits. And I forgot to say that, when I rebuilt the 196 engine, and got that pic of the head, the engine only had 20 hours on it.

 

[JTSpeedDemon]

I pulled off the front wheels to measure the bearings, inspect them, and see if they were flanged so I know what kind to get.
I made a shocking discovery!
The front right outer wheel bearing is the wrong size!!!

It's 3/4" ID instead of 5/8"! It corresponds with the tread wear, since it effectively gave it negative camber! The bearings are trashed as I thought, but the wrong sized bearing is the biggest problem. Gotta fix it!

 

[J.S.@SMS]

I had that on one of my karts. But somewhere it got a bushing that was 5/8 id 3/4 od (It was pretty thin). Previous owners and their riggery.

 

[JTSpeedDemon]

Yup, riggery. Or poor quality control somewhere in the assembly line. Probably riggery.
The outer face of the bearing is all smooth, like it's been hit with a hammer, so yup, riggery.

 

[JTSpeedDemon]

Ok, a set of 4 proper sized snap ring high speed sealed ball bearings are on the way from OMB Warehouse!
Then I can finally take it out for a test spin again!

 

[J.S.@SMS]

Ah the test ride, possibly the most stressful rides I've ever gone on. Of course I'm stopping every 2 minutes to make sure no bolts loosened up. I had the sprocket on the drifter loosen up, making it throw the chain every 20 seconds, and key fell out out of one of the wheel hubs. I'm just glad that GPS threw in 2 extra keys. And I had a front wheel fall off the streaker after I swapped the new wheels on. So I'm a bit paranoid now.