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Happy New Year everyone.
Got up this morning and did a whole lot of nothing for a long time. Sat around sipping coffee and taking it easy while relishing in a 31-0 victory over Ohio State. Now looking forward to a rematch with Bama.

Anyway, went out to brunch with WD, Baby Girl and Boo. When we got back I sneaked out to the garage while Wifey Dearest wasn't paying attention and pulled the heads.

Here are shots down the jugs and tops of pistons.







I don't see any scoring on the cylinder walls. Running my fingers over them they feel smooth. Mic'd at 71.5 mm with less that .1mm out of round.

I think I'll pull the jugs so I can finish inspection and measure the pistons and skirts. Hopefully all that's required is a set of rings.

Plan to sneak back out there in a few minutes to pull the reeds. Just have to catch WD not paying attention.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

Limped out to the garage and pulled the reeds

First glance not too bad



but on closer inspection
Broken corners on #1 and #2, the jugs that are giving me the most problems going cold.



Removed the starter, then nuts holding the jugs. Had to take a break.
Hopefully will pry the jugs off before the sun goes down.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

Last update for today.
I limped back out to the garage and pried the jugs loose. No saving the gaskets, so I need to do some Amazon or ebay shopping.
Anyway, here are piston pics. No obvious burns, no major scoring, mic'd in spec. Looks like they have been rattling in the jugs a little bit, but not terrible.

There are two pics, one each side of each piston









Tomorrow I'll remove the c clips, pull the wrist pins, and clean everything in prep for new rings and reeds.

Parts ordered, time to chill on the couch.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

Yup With that much carbon on the piston tops, that engine did not get regular ring changes.
Try polishing the top surface of the piston to reduce carbon build.
The pistons look stock? No modifications! Google piston mods for your motor. Reed valve engine builders would typically cut windows in the back side of piston to increase the intake duration. I've cut the complete back side out, but the piston is not going to last as long. Also speed secret #476, when ever you split the case add an 1/8" radius to all the edges leading into the transfer ports. Transfer ports need to have a 2 to 4 degree taper. If you have an iron sleeve, grind back the rear edge of the transfer ports. If its chome cylinder, use cratex rolls to prevent chipping. The under side of the piston is a good indicator of the tune, but just by looking at the tops, I would say you need to check cylinder heights and heads for the quench ban on all the cylinders. Two strokes need a tight ban, You only have one cylinder set correctly. I check to see if I can find an old SAE paper on two stroke quench clearances. Dave W

Not much work in the garage today as we had the buyer's and the home inspector over for about 3 hours doing the top to bottom inspection of Casa Busy.
When they were done I ambled out for a short stint.
I removed the stator housing and timing trigger plate, then started looking at how to pull the primary clutch. I need a big star bit that I'll borrow from one of the mechanics at work to unbolt the primary from the ring gear.
Next up was pulling the c clips and wrist pins so I could see the piston bottoms and get them into a batch to soak away the carbon.

This one has been pretty warm. It has had carbon build up that looks to have recently flaked off


This one was real warm


And this one was just about right


All parts are on order, so now I'm just kicking back waiting. Everything will get a good cleaning and I'll gently hone the cylinders to refresh the cross hatch before it goes back together.

THEN will be the task of finding the right jet sizes for a healthy motor.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

You are differently on the safe side for timing and mixture looking at the piston bottoms. You have problems when you start to see bubbles on the chard surface, that look like what you would see on a spark plug with a rich idle.
But I would guess that timing and mixture is not equal on all cylinders. Rule number one is timing. Being off just one or 2 degrees will make a big difference.
Need to verify all cylinders!
Are all the expansion chambers the same? Also "Check" float levels.
Be careful on the honing. 2 strokes are all over the map relative to cylinder finish. Some use a fairly low numbered stone while others are glass smooth. I'd check with the ring mfr.
I found the SAE paper. If you would like, it send me a PM with your address. Dave W

I didn't put a degree wheel on the motor, but I did verify timing by counting teeth on the ring gear. I've got 26-27 degrees BTDC initial timing and 10 degrees advance dialed in on the MSD box. Those follow the factory specs for the ZRT 800. I've had so much trouble with cylinders going cold that I haven't been able to verify settings with the timing light on anything except #3. Thankfully the flywheel has timing marks for each cylinder.

#2 pipe is a little longer to make the pyramid stack. I think that extra pipe makes a difference on jetting.

Will check, recheck, triple check float levels. Idle is way rich. There's something that I missed the first time through.

Will check on honing. I know what the book calls for, but not the ring maker. Hadn't thought about there being a difference.

PM sent.

Thanks for all the help.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

I could be off base, but 37* total advance sounds like way to much timing, but the pistons do not show any signs of stress. My guess is you need zero advance. For the honing, look at a quick de-glaze. Do not increase clearances. You need a lot tighter fitting pistons, then a 4 stroke. If #2 chamber's rear reverse cone is approx the same distance to the cylinder you are probably OK. Just judging by the pistons you may need to burn out the carbon in the expansion chambers. Dave W

Sorry, 10 degrees retard, so 27 to 17 between 4000 and 8500 rpm.

If #2 chamber's rear reverse cone is approx the same distance to the cylinder you are probably OK. What does this mean?

Yeah they need a burn out. spooge all over the motor and the garage floor.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

The rear reverse cone location, angle, and stinger outlet diameter determiners the reflection wave strength and RPM. If the chambers are difference between cylinders it will affect carburetion mixture settings at different RPMs ranges.
To keep wifey happy, do not burn out the expansion cambers in the garage
Do it out side. Dave W

Looking at the setup it looks like they did a pretty good job of accounting for the longer runner on #2 and moved the reverse cone to compensate. Of course I haven't picked up a 2 stroke exhaust tuning program, but I've started thinking about it. Could be a good time with my new TIG rig once we get into the new house.

I'll set up my propane burner (heat source for turkey frying, shrimp boils, and smoking pork shoulders) and propane torch for the burnout. I figure with the amount of liquid goo in there it could get quite interesting. It shot a nice fireball last week when #2 went cold for a while, then decided to spark again.

I've been asking similar questions over on the arctic chat forum. There's a guy with a race sled not too different from my setup. He mentioned the flat slide carb jets are a lot lower in the body than round slides, so smaller jets than the book calls for is pretty normal.
His race sled screams like a Banshee up to 9000 rpm running 330 jets, 035 pilot 1 turn out, 4 degree timing key, and aftermarket pipes.
I need to see if we're using similar needles.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

You alway want to start out 1 or 2 sizes larger jet, with new rings and or pistons on a 2 stroke. Once you have a practice session in, [20 to 30 miles] then you can start leaning down the mixture. You can easily seize a piston with new rings, because new rings will increase blow by until broken in, which reduces the oil on the cylinder wall. And DO NOT increase your oil to gas ratio for break in.
You can actual just shorten your current expansion chambers, to tune the engine for a 9000 RPM peak. May need to raise the exhaust port to match the higher RPM.
but I would ask on the other forum if they are using after market pistons and dyke rings.
If you are only turning around 7000 RPM you're better off with a wider ring. You should not see ring flutter at lower RPMs.
The rings have a pretty hard life sliding over ports, and not be able to rotate on the piston like a 4 stroke engine.
I would get some track time under your belt before you start modifying the motor. See if you can find a two-stroke Tuners Hand Book to give you some ideas. Dave W

Thanks Dave

Still waiting on parts to arrive. All my orders said deliver today, but the ship docs suggest Tuesday or Wednesday. I guess this weekend I'll be packing instead of rebuilding my motor.

I downloaded a copy of the tuners guide. Plenty to read in that one. I'll put a copy on my tablet and take advantage of some airplane and airport time I have coming up with work.

Soooo, I think I'll drop the 340s or 350s into the motor when I put it together and see if I can get it to run on all three cylinders when it fires up. Here's my starter setup

40:1 Redline racing oil in 93 octane ethanol free
035 pilots 1 to 1 1/2 turns out
350 mains
center clip on stock needle
135 starter circuit

27 degrees advance with 10 degrees retard 4000 to 8500 rpm

Belt on primary to secondary to have some load from turning the jackshaft and wheels even up in the air.

And I'll pray it runs well

Any special break in routine I should follow?

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

You're getting good advice from DaveW. My 2-stroke motorcycle days were mostly in the 70's which seem a little hazy now. I'm guessing I'll never get back to that collection of RD350s in the basement, too bad....



I think you should just run it till it gets warm once or twice, don't expect to be able to figure out any tuning without a load on the motor. The carb will not be running with the needle and throttle positions it would in real life for whatever RPM and power you are making. The risk is changing the setup after getting misleading results.

Make a metal lists of conditions that will win your races or kill your motor. Go down the list. Number one would be wide open throttle in your power band. Get that right and then go down your list. There will always be things ahead of testing the engine on jack stands. So don't learn what you don't need to know.

While it's open make a careful diagram on a sheet of graph paper of the actual port locations, sizes and shapes from TDC. Then hopefully you can check to see if it' stock or modified.

My motorcycles had a stock redline at 8500, after I had the cylinders ported and put on some pretty aggressive expansion chambers the motor pulled really hard to probably 12,000 or well after 10,000 which is where the tach stopped. It had a Dyke ring and used stock pistons. I started with some aftermarket units but they weighed more than the stock ones so I junked them, I think. No valve springs or floating valves to worry about.

The power band was such a big change for the motor that once it hit, if you suddenly decided to abort (from shear panic for instance) the power would continue to climb even while you were shutting the throttle as fast as possible. Just a moment mind you but it could be a very scary moment the first time.

Is 40:1 the recommended mix? When you change the oil mixture remember you are also changing the fuel mix so 40:1 is leaner than 50:1.

I used to use Permatex Aviation Form-A-Gasket to seal the cases after working on the motor. Maybe you are not going to split the cases.

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40:1 is the suggested mix from the manual. It was also suggested by the sled guys as enough oil in the mix for good lubrication without buildup in the bottom end.

I don't plan on splitting the cases unless I accidentally drop something down in there.

Hadn't thought about port mapping, but great idea.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216