Monday, April 20, 2009

Checking Spark Plugs

Since no one else seems to have anything to post, I'll continue.
Here's my luck with the new bike.
Friday, I go to check spark plugs before going for a ride and then delving into a potential air leak(surging at slow cruising speed). It's a two-stroke thing.
Right plug is galled from the start and i'm rolling out alu. threads with my pinky.
I'm tempted to just replace the plug but I pulled the right head.

Good thing I didn't just try to run it. BTW, this is called galvanic corrosion and it can happen to you too - anywhere there are dissimilar metals in contact.

I have a spare head but I had better pull the other to check both heads - in case that potential air leak was there.
Well one of the left cylinder studs came out of the block rusted to the sleeve nut!
Now I have to pull the unaffected cylinder to reinstall the stud correctly. I could have just screwed it all back in like a bolt but I'm a glutton for punishment!
Look what I see!

All this rusty grit falling onto the crank and into the case from all eight studs!

I found an RD350 gasket kit from a few years back (and a bunch of NOS cables I forgot I had!) so I can wrap this up this weekend.
Okay, that was easy. Now I see I have a missing exhaust stud. Made a new one. Looking at the rubber carb manifolds, I see they don't line up very well. Better port match those to eliminate that edge. A simple scribing shows the mismatch.

But look deeper. It's upside down but see how the iron cylinder sleeve has a lip at the intake port? I'll remove that while I'm at it.

Be careful as this is the intake valve of a two-stroke. Grind all the way into the cylinder, raising the opening even 1mm, and you can make the power very peaky. Modifying the height of the intake and exhaust ports is how you "recam" a two stroke. Simple to do but easy to make it unrideable.

Here you can see the port opened up.

You don't want to hog out the whole runner - just radius it at the offending part. I want to leave it rough in there as this helps with the fuel mix. Polishing intakes runners provided little gain and maybe even some loss. Also note how I ramped the cylinder sleeve to transition the runner to the port without a step. I never actually ground into the opening.
These things are how one would "blueprint" an engine. All is still stock but you gain all the possible efficiency possible before making other mods. The ports leading down into the crankcase can be matched as well BUT not without the case all apart so forget it. You 4-strokers will want to add a three angle valve job, a balance, and degree the cam.
Well I might as well pull the pistons, clean them properly and take a bunch of measurements. Regardless of the numbers, I'm not reboring this thing.

After hunting down a spare head in the shed, I decided I should paint the cyls and heads while it's all apart. See where this is all going?!
JP1 satin paint and bake at XXX for XXX minutes(turn off and go watch a James Bond movie). I like the new Bond as he kills indescriminately. The Walther PPK returns as well. Hey, anyone wanna go shooting? Anyway,

Common advice is to do this when the wife is away. My sis' redid her kitchen a few years ago so I combined her broken top and bottom ovens together to get one good one for the garage. Great for powder coating small parts - and this.
I had to sand off the fins but this is how it turned out.

Here's a before and after of the pistons.

3am. This is not to measure the rings but to show you the taper. These are known as keystone rings. The taper forms a wedge so that the cylinder pressure forces the rings against the cylinder wall. This also greatly reduces ring sticking.

New oils pretty much obviate the need for ring expanders. Both of mine in the top grooves were broken. I ended up leaving them all out even though I like to use castor-type oil. You 4-strokers can toss them all together. This is what the expanders look like.

Put the pistons back in before turning in.
Today, I broke a ring when reinstalling the right cylinder. Guess what? I'm now running one ring in the top groove of each piston! This wasn't my plan but was common in race motors of the time - this is my justification. And I'm NOT dumping $50 on stock rings when oversized piston/rings are $150. Not today, friends. Hack on! I have several other bikes to build before I go that deep on a new one!
Here she is back together. Not very snappy off throttle - needs some tuning - or is that just new blowby? ;)> Feels fine when gettin' on it. Break-in period? Screw that!

Thursday, April 9, 2009

"Pay no attention to the carb behind the side panel"

I don't know how many times I've heard guys say they are afraid to disassemble a carb. "I'll just take it to someone." $400 later, their vintage bike "runs great!" But what happens if it starts acting up again?

I dare say, knowing the basics of a carb is a right of passage for vintage bike owners. Some might say one has no business buying an old bike if they can't sort the carb - at least to stock configuration.
I won't go that far but guys, these are so simple, it's amazing they work so precisely! Sure, the new stuff intimidates - no, wait, irritates me, but these old Mikunis(typical on Yamahas) and Keihins(Hondas) area a cinch so insult yourselves no longer. If you ever built a model as a kid, cooked a complex recipe without an ER visit, or showered yourself without assistance you can do this. Most parts fit together only one way and usually you have another carb to reference. Mikuni's manual is available free online at Sudco's site and elsewhere. It's great info but I did a bunch before finding and reading it. Honestly, once you've done it, you will likely never need to read instructions again.
Here are the tools needed to completely "rebuild" a VM (round slide) Mikuni:

Playa please! A Phillips and small standard screwdrivers, a 6mm socket or wrench(main jet), and a 10mm for the float needle seat. That's it! Few specialty tools exist for most older carbs. Of course syncing them should follow but that's fun to do using a couple of WD40 straws or mercury sticks for you diaphragm guys(insert joke here). There's no doubt you will feel like your bike runs better even if all was okay. The simple adjustments alone might make things better.

The new R5 starts easily but won't stay running on a ride. Actually, the problem is mostly when braking and I remember something weird when using the signals(something foreign to me!) so it's likely a ground but I'm on a carb rant right now so..... Fortunately I enjoy working on these as much as riding them. Today Linda said, "I can't see you buying a turnkey bike." Touche'!

The battery reads 12.4V and 14.3V at 3000rpm (a quick and dirty battery and charging test). There was a loose wire at the battery but that didn't fix it. There's more to check on the R5 - plugs, coils, points, grounds, etc. but the carbs simply have to come apart on any old bike you pick up.

Side rant: Well, if I buy an older bike(pristine tank or not) and it doesn't have inline fuel filters, I can barely sleep until I have cleaned the carbs and put filters in there. It's funny how one symptom can mimic another system problem but that's an old bike for you - and carbs are often it. Cleaning them and reinstalling without filters is plain silly(been there). If you ignore this advice, you will either be best friends with an under-challenged mechanic or become proficient at cleaning your carbs - maybe even good at it on the side of the road in the rain.

Also, second to the, "I'll take it somewhere." is the, "I bought a rebuild kit...."
I'm no pro but with 2-strokes you become good friends with your carbs so I have disassembled, rebuilt, and/or modified carbs a couple dozen times and I have NEVER bought or needed a rebuild "kit". It's like paying for a "tuneup" on a new car with EFI and computer controlled ignition(what do you think they do?!). Anyway, perhaps there is a leak that could benefit from a new gasket but there is little in the kit that will make your old carb work better than cleaning and reusing the old parts. I have bought various jets or emulsion tubes(for mods or tuning) but I can't even remember buying gaskets - well maybe on the Bings(BMW)......... and Amals are gonna leak anyway! CVs are different - I would buy a diaphragm rather than repair one but there are tricks for that too.

This is not a tutorial but just a motivation. Spray carb cleaner is nasty stuff but works great. I just use my parts washer and a brush. If I had a choice between cleaner and compressed air, I'd go with the air. Combine the two and you definitely need safety glasses(I'm typing through misty glasses now). I take a mental note of the position of the adjusting screws - you can always return to that as a baseline although they might have been screwed with to compensate for dirt or poor tuning. I then disassemble, clean, then blow the cleaner out of all the orifices and jets. Takes maybe an hour but I've done it in 15min and I've taken a couple hours while listening to tunes. Don't be tempted to rush or to jam any metal tools into holes - especially the smallest ones(insert another joke here). Remember to be careful as these are pot metal and can mar easily. Don't scar up the carb body with pliers etc. If such coercion is needed, use a towel to protect the metal. Chasing a small orifice with a wire is a no-no as is drilling out a jet. I have coaxed crud out with the nylon bristles of a parts brush and have chased jets with individual bristles in the washer but that's it. If it won't come off with cleaner and a cleaning brush, it's unlikely to come off in use.

Finally, don't leave home without these.

I need to buy a bunch - I think I've picked them up at any dealer counter for about $1 apiece.

Don't be afraid of these things. If you have a problem there's lots of help online and that is what the KC cafe racers group is for........ at least give it a shot!

UPDATE: Rode on the R5 today to the dreaded Kansas inspection station manned by the cargo-pants wearing HiPo. No issues there but the bike started easier and ran much better too. Plenty of power and didn't die once. See! Still need to tune the ignition, etc. but what I thought was electrical wasn't at all. The fuel delivery was just too marginal - fuel fouling a plug or something. Dig in!

Tuesday, April 7, 2009

New Speedo

I put a digital speedo on the bike today. It is a 2" digital one. I am going to have to buy a universal sensor that mounts next to my sprocket to calibrate it. For complete pics, just visit my blog.

Saturday, April 4, 2009

What I messed with Saturday

Sun came out so I wheeled out the beast.

It's louder in person. I have a ways to go but last year's goal of Ralph Wayne's passed so maybe this year? May get laughed at but if I mow Ralph's lawn...........

Project "81"

Hello all,
I am a relative "newbie" to the cafe racer scene. I am currently working on a 1981 CB750. I'm trying to create a simplistic roadracer out of this DOHC CB. If you would like to follow the project, just go to
Welp, seeya later

Thursday, April 2, 2009

New toy

Obtained from another distinguished member. It is mostly original. Linda wanted me to have a "two-seater" for gelato runs so I added an R5 to fill the gap in my collection of the 350cc two-strokes Yamaha offered.

Most of the components are not only "usable" but are in great condition. I plan on removing the mirrors, swapping to lower euro-style bars, new tires, and some fork and seat work.

Low enough miles that the recommended head decoking isn't even required yet.