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Another One.. 2Cyl 2-Stroke Content
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Author:  95naSTA [ Mon Jul 24, 2017 11:57 am ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
I think it's mainly in the aftermarket ignition system. The plugs were in rough shape too.

Ordered a bunch of crap for fueling and clutch. I gotta get my oil tank hooked up too.. Next milestone is getting this thing moving.
Author:  Sirius [ Tue Jul 25, 2017 9:07 am ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
Did you go with an electronic ignition? (I assume the original Yamadog ignition used points).
Author:  95naSTA [ Tue Jul 25, 2017 10:16 pm ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
Yep! I swapped out the generator/points/condenser for a magneto/CDI setup. I really wanted this bike to have the least amount of components as possible.
Author:  Sirius [ Wed Jul 26, 2017 9:11 am ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
Out of anything you do to that bike, ditching the points may have been the best move. Those things can be so problematic.
Author:  95naSTA [ Fri Jul 28, 2017 8:55 pm ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
Got the forks swapped, rearsets on with the brackets I had water jetted, and made a petcock block off plate to fill the tank with evaporust. The fueling and clutch stuff didn't make it here before the weekend.

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The new brackets did require some clearancing.. Not too bad though.
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Author:  95naSTA [ Mon Aug 07, 2017 10:17 pm ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
I got some parts in the mail today so I squeezed in some progress.

I've been soaking the inside of the tank with evaporust for over a week. I didn't really intend on letting it soak for that long but it took longer for the Caswell coating kit to come in than expected. Here's what the clear evaporust looked like after..
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Protecting the tank
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Inside
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Cleaning and swapping seals on the petcock.
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I was sure to blow out the connector tube nipples and the petcock area that I drained the excess sealing resin through. I'll let it set for a few days before I do anything with it.
Author:  Sirius [ Tue Aug 08, 2017 9:31 am ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
That actually cleaned up pretty well. Judging from the pitting inside the tank there must have been a fine buildup of corrosion. I'd still run an inline filter between the petcock and carb(s).
Author:  95naSTA [ Tue Aug 08, 2017 10:44 am ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
Yeah the tank was in bad shape..

Do you still think the filters are necessary with the petcock strainer and a sealed tank?
Author:  Sirius [ Wed Aug 09, 2017 9:41 am ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
While you'd probably be OK, a small in-line filter is cheap insurance to prevent a farfel getting into your low-speed jets (e.g. idle jet) and messing with your idle/low speed performance. Obviously its not catastropic if that happens - just gotta pull the carb(s) and blow out the jets & passages - unless your out on the road, miles from anywhere, when it happens. (And you know that's when it will happen.) :eek2:

One of those little plastic Uni Filters is probably about $5 or less. Get the kind with the bronze-looking filter element as opposed to the screen type. I think they filter better.
Author:  95naSTA [ Wed Aug 09, 2017 12:58 pm ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
Gottcha. Appreciate the input as always.
Author:  95naSTA [ Fri Aug 18, 2017 6:51 pm ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
So this thing moves under its own power now.

I cleaned the carbs and reassembled them with parts included for a mod called the Dave F mod. It basically turns the carb into an older style carb and improves throttle response mid-range. It gives you a bunch of main jets and I decided to try 200 mains.

I fired it up and tried to see if I could get the clutch to engage but no go. So I ripped it apart replace the clutches and steels and any seal I could. So the pushrod, kickstart, and pump seal all got replaced. Another right cover that was in better shape went on at the same time.

Once that was all back together I kicked it and try to get the clutch to engage and no go. So I took the left cover off which also has a cam driven mechanism that pushes the push rod through the engine and disengages the clutch. With that off the clutch was engaged. So something's going on where I have too much length in between that mechanism and the clutch. In the spirit of wanting to get this thing moving under its own power I just threw a washer in between the cover and the engine tighten it down and it worked. I took a bunch of the laps around my neighborhood just to see where the fueling was and it needed some work.

I screwed around with the air jet to see if it would help and it didn't really do anything. I thought I had different pilot jets in this extra carb rebuild kit that I bought but they were the same size as was in there. I pulled the plugs and they were literally soaking wet so I switched the mains down to 190s. Got it all back together and took it for a spin but it still seem to be breaking up around 4k. I screwed around with the air screw for *shoot* and giggles but again didn't help. I know the air screw has little to do with the main jet but I gave it a whirl anyways.

I'm going to see if I have smaller pilot jets laying around somewhere and try those out. I might even put in smaller mains because if it's limited at 4K it's got to be either the needle clip or the main jet size. The other thing is maybe my timing is off but I'm pretty sure I got that thing locked in real good.

We shall see.

Edit -

I checked the new plugs and they were also wet. I did a bit of reading and it seems like rpm limiting is either lean or timing. Since I know that I'm definitely getting fuel, I'm going to try to set the timing again. I took a look at the pilots that came in the carbs (RD400 carbs.. found that out the hard way) and they're 25s. Stock RD250/350 carbs use a 27.5. I cleaned them up and might try them if the idle is crap after I mess with the timing. I think I may need 27.5s though.

Editx2 - Found that the clutch push screw is adjustable.
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Author:  95naSTA [ Sun Aug 20, 2017 2:18 pm ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
The timing was definitely off.. it was about .5 mm BTDC vs 1.8/2mm. The bike seems to be moving a bit better and not stuck at 4k. It does seem limited at 6kish now but seems ok with less throttle. From what I've read, that sounds more like fuel. I'll probably put the 200 mains back in.

My pilot jet is definitely too big though. With the air screws 2 turns out, I need to screw in the idle screws basically all the way in for it to idle. The choke makes it worse. I ordered the next step down, 27.5s.

The clutch adjustment was an easy fix.

I went to wire up the lights to the CDI lighting circuit and got nothing.. I tested the lights with a power probe and they worked fine, then I tried powering through the voltage regulator and no issues there. I tested the voltage at the CDI output and there was maybe a half a volt.. I think I'm going to have take the CDI unit off and look for pinched wires.
Author:  95naSTA [ Sun Aug 20, 2017 11:50 pm ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
No luck finding pinched wires or anything on the powerdynamo unit. I'm reaching out to 2strokeword.com folks for more pointers.
Author:  Sirius [ Thu Aug 24, 2017 9:39 am ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
95naSTA wrote:
My pilot jet is definitely too big though. With the air screws 2 turns out, I need to screw in the idle screws basically all the way in for it to idle. The choke makes it worse. I ordered the next step down, 27.5s.
Didn't you say you had a #25 pilot currently installed? If you're trying to lean it out wouldn't you go with a smaller pilot, like 22.5 or so? Or do these carbs go opposite the standard convention that bigger # = bigger hole (= richer jet)?

What happens if you turn your air screw(s) out to 3 or 4 turns?
Author:  95naSTA [ Thu Aug 24, 2017 5:21 pm ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
Sorry, I think I left out that part. I bought 30 pilots and started with those. I went to try the pilots that cam in my RD250 carb rebuild kits but they were also 30s. 25s came in the carbs when I got them and I ungunked them but thought I would just take a half a step down to 27.5s.

I'll have to try more than 2 turns out but from reading it sounds like you only want 2 max.

I contacted the vendor of the powerdynamo to warranty out the stator. Hopefully that goes smooth.
Author:  Sirius [ Mon Aug 28, 2017 10:05 am ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
95naSTA wrote:
I'll have to try more than 2 turns out but from reading it sounds like you only want 2 max.
I think 1 1/2 to 2 turns out is ideal, but if you can clean up the idle by going in or out more turns there's nothing wrong with that. If you can screw the mixture screw all the way in and the bike doesn't blubber or die (assuming an "air screw" as opposed to a "fuel screw"), then your pilot jet is probably too lean. Conversely, if you turn the screw way out and the engine doesn't start to race and ping, your pilot jet is too rich. At least that's the way I've always bracketed the jetting.
Author:  95naSTA [ Fri Sep 01, 2017 10:24 pm ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
Gottcha on the pilot. That makes complete sense.

Last week I plumbed in a re-purposed oil catch can for the 2-stroke oil reservoir. I had to plug a couple of the holes, drill and tap the one side for an outlet, threw a vent I found on mcmaster in the one hole, and I'm using the original in/out as a level indicator of sorts. I'll probably revisit that.. It took a while to bleed even after I gravity bled it to the pump and yanked the cable so the pump was seeing WOT. But after a while I was seeing oil at the carbs.

Currently I have a really bad drop in power at around 5k. I figured I would put the choke on around then and see if it helps. Well.. When pegging it at 5k I noticed it was slowly creeping.. and at around 6k it took off like a freaking rocket ship. With or without the choke, it's the same thing. I did a bunch of reading and more or less using pod filters instead of a y-boot and single filter is too short of a length and it'll create a pressure wave in the wrong direction at 5k. Other flow mods made it worse apparently. Some say the flat backed uni filters will make it worse since the wave has something to bounce against so I tried all foam filters but they netted the same results. I did some more digging and found that RZ350 manifolds with a crossover tube will trick the harmonic into thinking the intake volume is longer/larger and help. Which makes sense.. kinda like a couple variable intake manifolds I can think of. I'm waiting for these currently.

I also figured out what was going on with the powerdynamo and got the lights working during the week. Kinda dumb mistake by me where the AC input wires were too close in a connector and either arcing or shorting before the regulator.

Today I rewired everything with pinned connectors. I was never a fan of the bullet style.. I wanted to wire in the RD350 right controls for at least a kill switch and I also wanted to wire in the key tumbler. The only way the circuit connects on the kill switch and the key tumbler are opposite of what you would want. Off on the tumbler and OFF on the kill switch. Same for right light switch. I figured whatever, maybe it'll keep an idiot at bay. I liked the light switch for how close it is to the thumb so I made that the kill switch and I made the OFF/RUN/OFF kill switch the high beam. The running lights are on whenever the crank is spinning. I still have to put in a brake switch. I'm looking at at least throwing in a normally closed magura switch in the rear brake bracket.

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The wife came home in time to hop on for the last pic.

Oh and Hagon rear shocks are on order, as well as some repro tank badges.
Author:  Sirius [ Mon Sep 11, 2017 9:38 am ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
"I also figured out what was going on with the powerdynamo and got the lights working during the week. Kinda dumb mistake by me where the AC input wires were too close in a connector and either arcing or shorting before the regulator. "

Good find. Those kind of things can make you chase your tail forever. Electrical problems can be the worst.

2-strokes are rather sensitive to changes in exhaust and intake pressures and can be tuned to run quite differently depending on what you want to do with it. Machines used in high rpm environments like an MX bike or your road racer respond well to "expansion chambers" that help scavenge out the exhaust while maintaining the required back pressure to "close off" the exhaust port so your fuel charge doesn't just blow out through the exhaust. Unfortunately there is a trade-off, typically in bottom-end performance. My trials bikes do not use the typical expansion chamber design because of the poor low-speed response. Of course they sacrifice at the top end, but those bikes are not designed for sustained WFO operation. It's interesting that your intake configuration seems to have affected your upper mid-range performance.
Author:  95naSTA [ Mon Oct 09, 2017 9:41 pm ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
I was able to fix the 5kish flat spot with RZ manifolds and a crossover tube the other week. I think that's when I slapped some repro Yamaha tank badges on too.

Today I threw on new tires, Avon AM26 front and BT45 rear, new front EBC brake shoes (did the rears already), an aftermarket Halogen headlamp, YZ125 reeds, a boost bottle and some Hagon rear shocks.

The bike is a complete blast to ride. The powerband with the expansion chambers is tight and high but honestly that's what makes it fun. When it gets on the pipe it really feels like it has no business being that fast. And as long as I downshift into the powerband on the highway the thing scoots with passing power.

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Author:  Sirius [ Wed Oct 11, 2017 9:43 am ]
Post subject:  Re: Another One.. 2Cyl 2-Stroke Content
:coolmofo: Cool. When does it come on the pipe, about 6k rpm?
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