There She Blows

[bob58o]

10 BTDC doesn’t seem all that far off comparing to this table from like page 3 or 4 of this thread.

Thank you 65ShelbyClone

If this engine will knock, it’s most likely to happen at low rpm’s, so I think I have to tune ignition timing to prevent detonation at low rpm, which probably will leave power on the table in the upper range.

 

[bob58o]

Ok no more key.

Now I’m about 16* BTDC (+/- 1*)

If the corn juice can’t handle it, then I don’t know.
Can’t find the timing light, so I have to eyeball timing mark.

It fires about here…
And that is about 15.5* BTDC

I’m not sure exactly where my mark is using a Kohler flywheel and a tilotson ignition coil.

 

[bob58o]

This is a screen shot from the timing light video shows where the plug fires with relationship of coil and magnet on a gx200

 

[bob58o]

I guess I’ll try 10W-40 synthetic oil? Maybe 15W-40, which for some reason seems to only come in diesel oil variety.

I think standard oil for 196cc utility engines is 10W-30. Someone on the internet once said you should increase weight to 15W-40 for something like a blown e85 build if you were using 10W-30 NA on reg gasoline.

Who’s got a favorite type / viscosity of oil for me to use and why?

Unfortunately, this Bob is not the oil guy.

 

[bob58o]

All dressed up with no date for the dance. I’m not sure what I did in that one spot where I’m missing 3/4” of threaded bolt hole. Speaking of holes, the one in my old fan shroud is now gone.
Clean sleeper look. Lol

 

[bob58o]

Been a while since I set valve lash. If Doug was still here he’d be sure to remind me to set lash on TDC of the compression stroke.

I would normally try for zero lash when cold, but I’ll probably try for 0.003” on the intake and 0.005” on the exhaust.

Intake uses 5.260” pushrod with the 1.2 ratio roller tip rocker arm.

Exhaust uses 5.440” with the stock rocker arm.

 

[bob58o]

I’m sure I’m forgetting some things but it’s starting to look like an engine again.

Photo with both pulleys on the crank.

Ill start taking a carb apart to look at, drill jets, gab on that for a bit.

Piston Ring Gaps 0.015 - 0.016”
Ignition Coil Air Gap 0.015”
Ignition Timing ~15.5*BTDC
Spark Plug Electrode Gap 0.035”
Intake Valve Lash 0.004”
Exhaust Valve Lash 0.005”

 

[Denny]

I wish Poboy ( Doug) was still around.
And Chancer (Eric) and Bbqjoe. Them guys were a hoot!

 

[BaconBitRacing]

I wish Poboy ( Doug) was still around.
And Chancer (Eric) and Bbqjoe. Them guys were a hoot!

Sadly this is how forums go… old guys leave new guys come in.

 

[ezcome-ezgo]

GAB is a must

 

[bob58o]

Going to attempt to get it running with the 30mm carb.

The stock pilot jet (or at least the jet that was inside) is size 38.

Area of 0.038 diameter circle =
3.14159 * 0.019 * 0.019 =
0.00113

Adding about 35% area….
0.00113 * 1.35 =
0.00153

0.00153 = 3.14159 * r^2
r^2 = 0.00153/3.14159
r = SqRt(0.00049)
r = 0.022

Diameter = 0.044

So swapping the 38 pilot jet with a 44 jet will increase the area of the opening by 35%.

I guess a 35% larger area orifice doesn’t mean 35% more fuel but I guess it’s a place to start. I don’t think I have a 44 jet but I do have a 45, so size 45 pilot jet is going in.

 

[bob58o]

I guess I’ll show you my emulsion tube. And my needle tip.

Main jet installed was a 125.
I had something like a 205 in this engine when it was last running with the 21mm carb. The intake I was using before recommended something like a 190-200 when on gas.

I’ll have to see what jets/drill bits I have and meditate on what size main jet I should start with. Tune with feeling. Go fatter until ancient ancestors tell you to stop.

 

[bob58o]

Anybody know why one might use a longer main jet vs the shorter one. I’ve done a minimal amount of research on this subject and don’t really know. I have both kinds but need to do some searching to find the rest of the main jet collection.

I guess a longer jet is like changing float height???

 

[65ShelbyClone]

Which one is original to the carb model, main jet holder, and needle? Jets R Us has tons of information on that.

I guess a 35% larger area orifice doesn’t mean 35% more fuel but I guess it’s a place to start.

Yes it generally does and that's a legitimate way to make the estimation. People that mistakenly go by jet number(in Keihin's case, diameter) wonder why a 35% increase gives them 82% more fuel.

 

[bob58o]

The carb is Chinese knockoff of PWK so it probably uses a combination of Chinese knockoff parts. Some knockoff mukini parts. Some knockoff Keihin parts…

Which one is original to the carb model, main jet holder, and needle? Jets R Us has tons of information on that.

Yes it generally does and that's a legitimate way to make the estimation. People that mistakenly go by jet number(in Keihin's case, diameter) wonder why a 35% increase gives them 82% more fuel.

The one I pulled out of the carb was the short one and the largest short one I can find in my set is 150.

I was just wondering about tuning with float height. Not something I really ever messed with.

A longer jet might be like a float set “high”

A shorter jet might be like a float set “low”

Just an idea in my head.

“A low float height makes the bike run rich and a high height makes it run lean. If the float does not measure to spec, adjust it by bending the tang up to allow a higher float or down to lower the height.”

If this is true, I think I want the shorter jet to begin with.

How To Adjust Float Height | MotoSport

Read How To Adjust Float Height on the MotoSport blog and find more expert tips, product reviews and race recaps for each round of Supercross and Motocross.

www.motosport.com

 

[bob58o]

Let’s raise that needle by lowering the clip one slot. I might should have gone two slots. No clue what this engine is going to turn in the future. Maybe part throttle transition isn’t the most important right now.

 

[65ShelbyClone]

“A low float height makes the bike run rich and a high height makes it run lean."

Whoever said that has it completely backward. Lowered = leaner, raised = richer.

Imagine the column of fuel in the jet circuit above the level in the bowl. It has mass and gravity pulls it downward. The higher the bowl fuel level, the shorter that column is and the less vacuum it takes to pull fuel through the jet. The length of the jet/holder/needle guide won't change that. I would probably run a longer jet just to hedge against effects of fuel slosh or bowl level provided there is enough clearance in the bowl to not restrict flow.

 

[bob58o]

I had a bunch of the shorter jets with duplicates and I drilled a few out.

5/64” = 1.98 mm = about 198 jet size, but my drill bit measures closer to 2.08mm and I probably wallered out a bit, so it’s probably a 215 jet.

3/32” = 2.38 mm = about 238 jet size, but the drill bit measures closer to 2.45mm, also wallered a bit so calling this one 250.

I put the fat one in there for now. I wonder if I have an 11/128th bit somewhere?

 

[bob58o]

Unless I don’t have the jet holder / E-tube in all the way, the bottom of the short round jet extends past the gasket surface and into the bowl drain plug. They’re probably only a few mm’s of space between the jet and the plug.

The longer hex jets are like 8 or 9 mm longer. They wouldn’t fit, or I would need a deeper bowl drain plug. That’s too bad because the longer hex jets come in a 10 pack ranging from 200-250 for like $10 on eBay.
Those aren’t the pilot jets no matter what the person selling claims.

 

[bob58o]

Going to have to tweak the location and belt length/tension
And come up with a sturdy mount.