Author Topic: 1972 CB500 - Rebuild Project (Read 30825 times)

Puffin · « **Reply #175 on:** April 04, 2016, 01:22:53 am »

Carb Sync attempt #1

Ok so made a first attempt at trying to vacuum sync the carbs but I'm having a little difficulty and could do with some help from the carb gurus please.

I can get the bike to run at about 1500 - 1800rpm with the choke fully open however I can't get the bike to idle or run with the choke closed. At these rpms the guages are showing the carbs to be fairly well balanced.

As soon as you close the choke the bike dies even if you try and hold the throttle open and increase the rpm.

Question - If the bike wont run with the choke fully open that means there is an issue with the idle fuel circuit correct? i.e. with the butterflies fully open it's getting too much air and not enough fuel?

I'm thinking that maybe the fuel level is too low in the float bowls? I checked back in this blog and I wrote that the fuel level was about 5mm below the float bowl gasket.

Any thoughts before I start removing float bowls?

Puffin · « **Reply #176 on:** April 04, 2016, 02:30:27 pm »

Ok after a nights sleep and a fresh mind I realise I'm being an idiot..!

Moving the choke lever to 'Open' is the normal running position. I was getting confused and assuming 'Open' was the cold starting position when in fact the opposite is true.

This is why you shouldn't leave a project for 6 months and come back to it... your brain rids itself of useful information.

Take 2 tonight

Stev-o · « **Reply #177 on:** April 08, 2016, 07:32:29 pm »

Choke positions can be confusing to some at times, you got it now, off = open.

Puffin · « **Reply #178 on:** April 11, 2016, 07:47:52 pm »

Carb Sync attempt #2.

So I had another go at dialing the carbs in last weekend but I was still not happy. I could balance them ok but the bike just wouldn't idle correctly... it would gain rpms and then suddenly drop and stall and it needed more than 1100rpm to get it running. Again turning the air screws didn't seem to make any difference.

I decided to go back and make sure everything else was ok before trying to diagnose carb issues.

1) Checked cam chain tension - ok
2) Checked valvle clearances - Too much gap, particularly intake valves.... I had set them before the first start of the engine but they needed adjusting now that the engine had run. I reset them to factory specs and will keep an eye on them. I guess these will settle down once everything beds in?
3) Checked timing - Seems spot on. Test light comes on exactly on the full advanced marks on both 1-4 and 2-3 (Dyne electronic ignition)
4) Spark Plugs - All spark plugs were completely sooted up. This would indicate rich running condition correct? I assume that these bikes run slightly rich at idle and I had been idling a long time trying to tune it in but surely this is too much?
5) Float bowl levels - Seem pretty good
6) Compression - All 4 cylinders even at 110 - 115 psi

Stev-o · « **Reply #179 on:** April 11, 2016, 07:51:26 pm »

That plugs appears extreme rich condition, something is not right. What jets do you have?

Puffin · « **Reply #180 on:** April 11, 2016, 07:54:38 pm »

After checking the float bowl levels I think I may have found the problem...

I noticed some crap come out with the fuel as i drained the bowl. when I took the bowl off I was pretty horrified to find this...

Puffin · « **Reply #181 on:** April 11, 2016, 08:06:33 pm »

If a bit of this loose crappy material has got stick in one of the jets or is clogging up one of the passages it might account for my issues.

Everything was absolutely immaculate when I put it together so I can't believe there is this much crap everywhere. The carb bodies almost look like a chemical reaction has taken place. Some looks like jelly, some like rust flakes only I don't think it is rust. I checked the pet-cock bowl and filter and they are both spotless so it's not coming from the tank.

The only thing I can think of is that the fuel has reacted with a chemical cleaner I used to clean the carbs but i'm sure i just used proper carb cleaner or standard engine de-greaser.

Either that or I used some dodgy old fuel.. I did have some 2-stroke fuel mixed in a can in the garage and I might have done something stupid like run that through the carbs months ago when I first checked the fuel levels in the float bowls. Would old congealed fuel with 2-stroke oil in it leave this mess behind if you let it sit a few months?

Stev-o · « **Reply #182 on:** April 11, 2016, 08:29:52 pm »

2 stroke oil could cause plugs to look rich but not corrosion. Are you sure your tank is clean? Drain some into a clear jar to inspect.

Puffin · « **Reply #183 on:** April 11, 2016, 09:00:38 pm »

Quote from: Stev-o on April 11, 2016, 07:51:26 pm

That plugs appears extreme rich condition, something is not right. What jets do you have?

Everything stock except I replaced the slow jets with aftermarket ones of the same size.

Puffin · « **Reply #184 on:** April 11, 2016, 10:43:11 pm »

Quote from: Stev-o on April 11, 2016, 08:29:52 pm

2 stroke oil could cause plugs to look rich but not corrosion. Are you sure your tank is clean? Drain some into a clear jar to inspect.

Yep I'm pretty sure it's not the tank but that is a good idea to rule it out completely.

calj737 · « **Reply #185 on:** April 12, 2016, 03:45:10 am »

Also, your fuel level is too high according to the picture you posted with the Clear Tube. It should be 3-4MM below the seam. That will cause the rich condition at idle.

Looks like you need to re-clean the carbs

Puffin · « **Reply #186 on:** April 12, 2016, 05:13:09 pm »

Quote from: calj737 on April 12, 2016, 03:45:10 am

Also, your fuel level is too high according to the picture you posted with the Clear Tube. It should be 3-4MM below the seam. That will cause the rich condition at idle.

Looks like you need to re-clean the carbs

Ok thanks Cal, easy to re-set these now that I have to take the carbs off again for cleaning

MickB · « **Reply #187 on:** May 01, 2016, 06:59:52 pm »

Maybe you can just take the bowls off and clean them and pull the jets out and leave the rest insitu, if you take the aircleaner boots off stuff some rags in the throat of each carby or if you prefer each orifice and use a mirror and a Dremel with a wire brush on a flexible cable like a dentist.

Cal'll have a comment after this suggestion for sure.

MickB · « **Reply #188 on:** May 02, 2016, 02:45:50 pm »

If it's the photo I've seen with all the corrosion take the carbies off.

Puffin · « **Reply #189 on:** May 09, 2016, 09:20:33 pm »

Quote from: MickB on May 02, 2016, 02:45:50 pm

If it's the photo I've seen with all the corrosion take the carbies off.

Yep I elected to take the Carbs off and give them a proper clean. Whilst off the bike I re-balanced all the throttle bodies and adjusted the float levels as per Cal's suggestion. I managed to get the fuel level to 3-4mm from the gasket line on all the carbs... at least I think I did, every time I re-checked they seemed to keep changng but I'm fairly confident they are about right.

I knew my old Air Box boots were on the way out and two of them split whilst I was taking the carbs off. I stumped up and bought a nice new set from 4into1.com. Whilst I was at it I got another side-cover badge to match the one I already had. These reproduction badges are quite different from the originals so having one of each just didn't look right.

I think before I put the carbs back on I'm gonna get the rear hoop welded on. Just need to find some time to cut the end off and plan where I need mounting tabs for the seat, indicators and possibly a small rear fender.

I'm finding it hard to find the motivation to finish this off which is a shame because I really want to get out and ride it... I think I just need to get a little done and then it will start flowing again.

rosewood · « **Reply #190 on:** May 10, 2016, 06:33:45 pm »

Head up Puffin...

Come have a look in my garage and you will realize how close you are to the finishing line...

I have ended up following your foot steps motor is out of the frame being torn down needing new primary chain etc etc..alot more work than I was anticipating

rosewood...

MickB · « **Reply #191 on:** May 16, 2016, 04:49:01 am »

Puffin loved the tube with the right angle to check the levels, what about putting it in tips and tricks.

Puffin · « **Reply #192 on:** May 22, 2016, 08:53:11 pm »

Got a random email the other day from somebody who knew I was restoring an old Honda so I went down to meet them and I ended up salvaging this old girl out of a shipping container on Sunday.... she is now sitting in my garage waiting for me to finish the CB500. I hadn't planned on taking on another full scale project but I guess when these bikes turn up randomly you need to snap them up if the price is right.

CB350 Four, first registered in NZ in 1974, 99,500kms on the clock. She seems to be all there except the left hand switch gear. I don't think the paint is original as I believe they came in Red just like the spare tank you can see in the back ground, but she'll be getting a new paint job anyway.

She's definately old and tired and is going to be a lot of work again but she turns over ok and was ridden into the container a few years ago. I expect it will need a full engine rebuild after 100,000k and about 10 owners. The guy said the starter clutch has definately gone so I'm going to have to open her up just like the CB500 before I even get it running.

Came with a spare starter clutch, tank and lower triple clamp but given the amount of CB350, 500, 550 and 650 stuff the guy had I'm not going to be short of parts if i need them. Don't actually know anything about the 350's so will need to do my research but looks to be a scaled down version of the 500 so i'm off to a head start.

Thinking full on Black paint job including engine, frame, tank, fork ears and headlight bucket, polished chrome everywhere else, overbored pistons, visually quite stock except for upgrades to electrical system and lights, modern street tyres. Something classic looking.

Tews19 · « **Reply #193 on:** June 14, 2016, 03:22:09 pm »

Not sure if it was covered but check the spark plug cap resistance?

Puffin · « **Reply #194 on:** September 25, 2016, 07:38:20 pm »

Wow so it's been 18 months since I started this project and looks like I've not worked on the bike since April. I definately got a bit fatigued seeing as I've been at it so long so I've let it sit over winter whilst I tackled some over-due house projects such as a leaky roof and rotten joinery. Anyways with summer on the horizon and some friends out enjoying their bikes for the Distinguished Gentleman's rides whilst I sat at home with nothing to ride I've decided to pull my finger out and get back into it and get this thing finished off.

I'm going to set myself a challenge to have this done by 1st December

10 step plan as follows:

1) Chop Back End and de-tab old seat mounting stuff
2) Weld Seat Hoop on
3) Mock up rear end and work out where I need mounting tabs for mud guards, fenders, seat pan, indicator lights etc
4) Weld mounting Tabs on & paint everything back to black
5) Fabricate seat pan out of fibreglass
6) Get seat made by a professional
7) Install rear lights & number plate

Tune and sync
9) Get bike re-registered
10) RIDE!

Puffin · « **Reply #195 on:** September 25, 2016, 07:52:09 pm »

So steps 1 and 2 are completed.

Got the back end cut up and brought the bike into work where our friendly maintenance guy took some time out one evening and welded on the hoop which I got from Harisuluv on this forum. He cut a couple sections of box steel up and fashioned a couple of triangles to fill in the undersides of the hoop where it meets the frame and tie the back end in nicely.

He also gave me a few welding lessons and some advice and I got super enthusiastic and went out and bought a welder. Hopefully with a bit pf practice I should now be equipped to tackle the rest of the welding requirements on my own...!

I'll tidy up all the welds once I have a the final mounting tabs and cross member installed.

Puffin · « **Reply #196 on:** September 25, 2016, 08:08:53 pm »

I wanted to keep the internal plastic mud-guard in place to protect the electrics and try and keep road splatter off all my nice clean engine. It's well designed and fits better than anything I could fabricate and because I'm keeping the side covers you really can't see it at all.

The only issue was it used to mount on the fender mount 'arched' section on the back of the sub-frame that I just cut off.

Fortunately it slides in between 3 metal tabs and so I just slid a couple of Speed Clips over the tabs, drilled a few holes and held it together with some washered self-tapping screws. Holds it in place really well.

Puffin · « **Reply #197 on:** September 25, 2016, 08:38:01 pm »

So for the rear end I'm leaning towards 2 options:

Option 1 (as per mock up below) - Reinstall the original rear fender but have it so just maybe 100-150mm is sticking out past the hoop. (That's 4 - 6 inches for you 'mericans and Brits over 40!), Install a small single 'bates' style brake light on the fender and have a side mounted licence plate.

Option 2 - Have no rear fender, mount a cats-eye type brake light under the kick-up of the hoop. The plate can either sit under the light or be side mounted.

Thinking Option 1 at the moment... but I'm fickle so by tomorrow it could be some 3rd option I've yet to consider.

calj737 · « **Reply #198 on:** September 26, 2016, 04:23:58 am »

Definitely option 1.

Stev-o · « **Reply #199 on:** November 09, 2016, 03:44:48 pm »

Quote from: calj737 on September 26, 2016, 04:23:58 am

Definitely option 1.

+1. No fender on rear looks odd to me.

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Author Topic: 1972 CB500 - Rebuild Project (Read 30825 times)