Sunday, July 26, 2015

Cleaning out a fuel tank with vinegar

This is a followup to a previous post. Thanks for reminding me Shep.

The CB550 tank was a mess of rust and varnish inside so I used a mild acid called vinegar to clean it out. The vinegar sat in the tank for about 5 days and was shaken now and then to agitate it.

When I poured it out, it was yellow, gritty, and filled with fine chunks of rust and varnish. The inside of the tank looked like bare metal with brazing spots. It was quite clean and was enjoying a bit of flash rusting before I could take a good picture. Unfortunately, I wasn't able to get any before pictures, and the after pictures don't do it justice. There is an after picture below. 

So does vinegar work to derust a tank? 

Yes. I would say so.

Is it easier to deal with than say, MEK?

Umm. I shouldn't have to answer that, but yes. Yes it is. Vinegar doesn't cause skeletal birth defects. Also, it's easier to dispose.

Do you really have to wait 5 days for it to clean the tank?

I don't know. I didn't have time to check it for a few days but based on the results, I'd bet it would do a fantastic job in 48 hours.

Was it easy?

Filling something up and forgetting about it for a while is pretty darn easy. I can forget things without even trying.

Progress on the CB550

Carbs are cleaned and ready to be assembled, Ignition system is tuned up, and now I'm just waiting on parts so I can get the engine fully running.
In the mean time, I had to at least hear it fire up. So I sprayed some carb cleaner down the ports and gave the starter a spin. It ran for a few seconds.
Very happy.

Sunday, July 19, 2015

Mike's 1978 CB550. New Restoration Project

This is my uncles bike. He bought it new in 1978 down in North Carolina. He rode it around until the mid 80's and it was parked in his garage for the next 30 years. 

I would love to do a complete restoration on it but the amount of corrosion warrants replacing some potentially pricey items. So for now, we'll be getting it operational, repainting and managing the rust as best we can. New chrome might come later if I can find a nice set of pipes and fenders.

The cheap and lazy way to remove rust from a fuel tank

White vinegar and time. We'll see how this goes. The inside of the tank was spotted with rust and will need to be coated.

48 hours of vinegar with a few shakes now and then.

Updates in a few.

Saturday, July 18, 2015

New Jet Blocks for the VM29 Carbies

I've been spending a lot of time on these carbs recently. This is mainly because they were beat to death before they ended up in my hands. I got the rack for 75 bucks, which turned out to be about all they were worth. Damage inside and out.

Luckily over the years, these carbs have become more and more desirable and the once obsolete parts are now coming back. Gaskets, jets, screws, etc. Have been available but hard to find on occassion. But nothing was worse than the jet block.

The jet block is a cast piece that rests in the throat of the carb and makes the transition in the slide region smooth. It is obviously critical to the function and performance of this carb, but is also the weakest link. The area of failure is where the needle jet threads into the bottom of the jet block. The cast aluminum is soft and porous, making for fragile threads. Many people who have worked with these carbs have dealt with stripped jet block threads by boring the boss open, pressing a brass slug in, and retapping. This makes a better block than the original but it must be perfectly straight.  Others have just used epoxy to glue in the needle jet. This can also be tedious and it's not permanent. I ran a set with an epoxy-ed needle jet for two years and it was ok. Eventually it began to disintegrate even though I used PC-9, which is approved for fuel.  All these bandaids aside, there is a much easier way.

Z1 Enterprises has been making new billet jet blocks for a few years and they are quite nice. For about $40, you get a block that is nearly drop-in with stronger threads. Don't  forget to replace the small paper gasket underneath and clean the area well. The jet block must be centered well in the slide bore to avoid rubbing.

That being said, when I installed a new Z1 block, I used the small screw and the jet needle to get the new block seated as well as I could. With a few iterations it only has a minor bit of contact on the inside of the slide. It slides smoothly but witb a bit more friction than the others old blocks. I would expect that the interface will clearance itself a bit after some short use. I may mark the contact areas and polish the block where needed to prevent scoring on the slide.

Thursday, July 2, 2015

Bore Scoping a Couple of CB750s

I borrowed my friends bore scope just to poke around a bit.  Did I find anything interesting?  Ehh, I'll leave that up to you.  It's not the best scope but it was good for some more than basic diagnostics.  It was fun to poke around.

Here are a few shots from my 836 engine.  Ported head, oversized intake valves, and about 10k on it. The #4 cylinder burns a tiny bit of oil noticeable on startup.
#4 cylinder

 #4 cylinder.  Hone-y isnt it.


#4 cylinder
#1 cylinder.  More carbon.

#1 cylinder.

#1 cylinder
#2 Intake Valve

#3 intake Valve

The next engine is a 1978 F3 but the top end was rebuilt with K model parts.  No clue if it's any good. I found some debris, rust, and what looks like bad honing patterns. The #4 intake spigot is also broken but that's another story:
#1 cylinder

#2 cylinder.  Maybe has a little rust from sitting on the right side of the picture

#3 cylinder.

#4 cylinder.  It has some debris in it.
Ohh and I found a little kernel in the #4 intake.


Friday, June 12, 2015

Tuning Results: Testing a few adjustments on Rock Flute

I've spent some time verifying the settings on nearly everything for the engine. I also adjusted the compression on the rocker bolts for the front end.

First off, VM29 carbs don't have vacuum ports for synchronization so I added some. After the vacuum sync, the off-idle stumble is gone, idle is much smoother, and the throttle response is more crisp. A well synced set of carbs is paramount.

The plug gap was increased from .026 to .036. This made a huge difference in the heat of the plugs. They're running much cleaner and the exhaust note sounds a lot sharper. I'm going to bump up to .040-.045 soon.  There is plenty of spark energy to cross a bigger gap. The plugs should take the heat too. The resistor plugs have helped with noise in the Tachometer signal and should also help develop more spark duration. I am planning on testing out some 10 kohm Resistor caps to increase the spark duration. The duration on a dyna spark is about 0.9 ms. The stock points system had a duration of 1.5 ms and the cb operates best with a minimum duration of 1.0 ms according to the wisdom of Hondaman.  With the addition of a 10 kohm cap, I can run non resistor plugs and increase the spark duration by 15-20%.

I also verified the ignition timing and found that 1/4 was set to 39* and 2/3 was at 40*. Not a huge difference but certainly not good. I also noticed that the screws for the 1/4 pickup weren't very tight. After some thought, I decided to reduce full advance back to around stock so it's now set at 35*. I changed the timing curve to setting 5 on the Dyna 2000 which moved full advance up to 6500 rpm from 3500 rpm. When riding the bike after these changes, I noticed that the bike would load up easier at lower rpms. I think this might be due to the lack of timing advance below 6500 rpm so I switched the the timing curve back to curve 4. This curve has full advance coming in at 3500 rpm. More like stock, which works well for many differently built engines.

All in all, cleaning up the timing, opening up the spark gap, and synchronizing the carbs has made a significant difference in the behavior of the engine. It has a much smoother idle, easier start, smoother transition off-idle, and a crisp throttle throughout. The suspension adjustments have allowed the front girder to move easier and I'm running a lighter pressure in the air shocks. I will post an update after I do some testing to optimize the spark gap.

I also lubed up the cables and affixed the speedo pickup to the rear stay to reference the rotation of the rear sprocket. Road tests were done with a temporary fuel tank and no rear fender since the originals are out for paint. A bit awkward...and a bit illegal.