Topic: CB 750 Project 1 - Rides Well but a few tweaks needed

[timbo750]

G'Day Timbo, I've seen a guy demonstrating how to weld with those (or similar) alloy brazing rods at a couple of swap meets, and it was amazing, that stuff works bloody fantastic, so of course, I bought some, took it home, and couldn't get it to stick, but that's just my incompetence, and no reflection of the product.

My cuz used to fix lawn mower bases at his mower shop with it, and reckons it's the ant's pants. Having said all that, wouldn't it be easier to just buy a better head? Cheers, Terry.

I am going to do plenty of trials on both new old ali and my mate has old used head we can practice on.

I have thought about the option of buying another head but budget is starting to get tight so first option from now on is to fix first and replace when either critical or no other option. Also I have already done the porting work and cant bear to discard all those hours.

[krusty]

G'Day Timbo, I've seen a guy demonstrating how to weld with those (or similar) alloy brazing rods at a couple of swap meets, and it was amazing, that stuff works bloody fantastic, so of course, I bought some, took it home, and couldn't get it to stick, but that's just my incompetence, and no reflection of the product.

My cuz used to fix lawn mower bases at his mower shop with it, and reckons it's the ant's pants. Having said all that, wouldn't it be easier to just buy a better head? Cheers, Terry.  

I've used those rods for repairs. One I did was a broken switch block off a DT1. And also repaired a few holes in my tinny. That would have been at least 10 yeaqrs ago and the repairs are still good. I seem to recall the bloke selling them at the swap meet said don't use a steel wire brush to abrade the surface, don't know why, but I used a brass wire brush.
A while back my son's CBR250RR had a holed piston (bad fuel). The head was taken off and the hole TIG welded with the piston in situ. If you can, go for the TIG.

[timbo750]

I decided yesterday I would strip the paint of another tank I had to see if it would be an easier fix. This tank leaked when I tried to fix the rust with vinegar, I ended up with rusty vinegar all over the bench and floor but I could not see where I was leaking. Now that most of the paint is of the holes are very obvious. There must of been about 1/2 inch of water in the tank for a while as there is a line of rust pin holes, I was actually expecting small holes around the lower seem.

Now I know it is hard to judge without photos (I will post some tonight if I get a chance) but does anyone know what sort of hole can be filled with a tank repair kit?

I was also considering using silver solder to repair/patch the holes.

[SOHC4 Cafe Racer Fan]

I decided yesterday I would strip the paint of another tank I had to see if it would be an easier fix. This tank leaked when I tried to fix the rust with vinegar, I ended up with rusty vinegar all over the bench and floor but I could not see where I was leaking. Now that most of the paint is of the holes are very obvious. There must of been about 1/2 inch of water in the tank for a while as there is a line of rust pin holes, I was actually expecting small holes around the lower seem.

Now I know it is hard to judge without photos (I will post some tonight if I get a chance) but does anyone know what sort of hole can be filled with a tank repair kit?

I was also considering using silver solder to repair/patch the holes.

With pin holes, you may be able to braze them, but the metal will be so thin it is likely to melt through.  You are better off cutting out the rusted portion and welding in a patch.

[Retro Rocket]

Tim, how nice a tank do you want..?  You can buy brand new ones from Yamiya, painted or unpainted...

http://www.yamiya750.com/index.php?main_page=index&cPath=182_80&sort=20a&page=1

http://www.yamiya750.com/index.php?main_page=index&cPath=157_168

[timbo750]

I decided yesterday I would strip the paint of another tank I had to see if it would be an easier fix. This tank leaked when I tried to fix the rust with vinegar, I ended up with rusty vinegar all over the bench and floor but I could not see where I was leaking. Now that most of the paint is of the holes are very obvious. There must of been about 1/2 inch of water in the tank for a while as there is a line of rust pin holes, I was actually expecting small holes around the lower seem.

Now I know it is hard to judge without photos (I will post some tonight if I get a chance) but does anyone know what sort of hole can be filled with a tank repair kit?

I was also considering using silver solder to repair/patch the holes.

With pin holes, you may be able to braze them, but the metal will be so thin it is likely to melt through.  You are better off cutting out the rusted portion and welding in a patch.

I havn't finished removing all the paint yet, so once I have a will make a better judgement call, it may be too far gone.

[timbo750]

Tim, how nice a tank do you want..?  You can buy brand new ones from Yamiya, painted or unpainted...

http://www.yamiya750.com/index.php?main_page=index&cPath=182_80&sort=20a&page=1

http://www.yamiya750.com/index.php?main_page=index&cPath=157_168

yes I have been looking at them, very convenient buying something painted in factory colours but the budget will only allow those sort of purchases when there is no other option.

[Terry in Australia]

I was thinking I should change the title and remove the reference about the set backs, but not after this weekend.

Firstly I decided to remove the collar from the old swing arm in preparation for the new brass bushes. I don't know why I was so surprised to find it in the condition that it was in after everything else that I dealt with so far. Also it looks like someone chrome plated the swing arm with all the bushes and collar installed.

Then on Sunday I thought I would sand the tank and find out how much filler there actually was in there. The tank was in primer when I got it and I knew it had some filler but its now a lot lighter. I think getting this tank to reasonable condition will be a project on its own.

Hey Tim, is it a K1? I built a K1 "Custom" in 1980/81 when I was up in Sydney, and I bought a chromed swingarm from a shop in Paramatta Road, for 45 bucks.

They hadn't removed the bushes when they chromed it, and I didn't have the tools or skills to replace them, so I just installed it, and rode it like that for another 4 years before I sold it here in Victoria. I wonder if you've got my old bike? Geez I'll have to see if I can find a pic of the old beast!

As penance for my past wrong doing, I've probably got a better collar here if you're desperate. Cheers, Terry.

[timbo750]

Terry, no the frame is a K2 and the engine is K4, and I got it from Brisbane (so man time I wish I waited for something better)

I ordered a new collar from Yamiya $70, good price if you ask me. I actually asked a mate who is a machinist and he said by the time you put a radial groove and all the rest it would probably cost about $200 to make a one of.

I got my new German brass bushed yesterday, they look good and will test the fit hopefully on the weekend.

I got my brazing rods also, I know many sceptical but I am got test them first. my mate is very interested to see how they will work as they may save a lot of time doing minor repair work in his machine shop. he has plenty of old heads to try them out on and I am going to try and fix a broken top bridge as well - not for use but just practice.

[Retro Rocket]

Tim, how nice a tank do you want..?  You can buy brand new ones from Yamiya, painted or unpainted...

http://www.yamiya750.com/index.php?main_page=index&cPath=182_80&sort=20a&page=1

http://www.yamiya750.com/index.php?main_page=index&cPath=157_168

yes I have been looking at them, very convenient buying something painted in factory colours but the budget will only allow those sort of purchases when there is no other option.

Its relatively cheap Tim, if you work out the cost of a new tank and covers and getting them painted here, its a bargain...

[timbo750]

Retro, I will be honest that I have no idea how much the was actually going to cost but I was thinking only a couple hundred bucks as a guess. But if it is going to cost $400-500 then buying from Yamiya is worth it.

[timbo750]

Got the new collar from Yamiya,  I am always impressed by the quick delivery from Japan.

Started trying out the aluminum brazing rods. It is definitely the hardest to get right or even reasonable on the old cast ali. I have to repair a broken top triple tree for practice and stuffed the tree. I also tried on a cracked 6cyl it seemed to work ok once the head was hot enough.

[Terry in Australia]

From what I can remember about those rods, you don't apply heat directly to them, you heat the surface and then wipe it with the rods. The problem I had was I didn't get the surface hot enough, and so the rods would stick, then I'd get sick of it and apply heat to the rods, and just melt them away to nothing. Patience and technique is the key. Cheers, Terry.

[timbo750]

I done plenty of brazing copper and brass plumbing fittings as you said and with any brazing or soldering the parent material has to be at the melting temperature of the rod. As you may already know ali disipates heat very quickly so you have to so much more of the head just keep heat in the area to fill.

I can already see a befit of this over tig welding but for someone who can already competently tig weld they would most likely ask why bother.

[Terry in Australia]

I wonder if it'd work better if you pre-heated it in your oven first?

[timbo750]

Yes the oven would be good.  I did most of my trials at my mates workshop so no oven. He did tell me that if they weld a head they would preheat wil lpg to about 200c before welding. But he can't weld himself and doesn't have anyone working for him that can either so he is hoping I can work this out and teach him how to do it.

[timbo750]

Got the swing fitted and lower tripple. It felt so good to finally attach something to the frame. I still only have the old #$%*ty rear shocks and used one to hold it up. It looks so bad I will be buying new shocks very shortly, just have to decide on what to get.

[SOHC4 Cafe Racer Fan]

Got the swing fitted and lower tripple. It felt so good to finally attach something to the frame. I still only have the old #$%*ty rear shocks and used one to hold it up. It looks so bad I will be buying new shocks very shortly, just have to decide on what to get.

The IKONS made down under are great for the money.

[timbo750]

I have got prices now for both Ikon shocks and Hagon. They both have shocks that are of similar price but Ikon have a set with adjustable rebound, so my questions is if the rebound adjustment is worth the extra $187.

I will say though that although both look very well made, the Ikon look better, not sure why but they do.

[SOHC4 Cafe Racer Fan]

I have got prices now for both Ikon shocks and Hagon. They both have shocks that are of similar price but Ikon have a set with adjustable rebound, so my questions is if the rebound adjustment is worth the extra $187.

I will say though that although both look very well made, the Ikon look better, not sure why but they do.

Timbo,

I have the IKONs on my 750, and I'm pretty happy with them for street riding.  I also have Hagons on my 550.  I think the IKONS are a step up.  I guess it depends on how you are planning to ride your bike and whether the extra adjustability warrants the extra coin. 

[timbo750]

I am planning on keeping this 2up as the wife and kids want to go gor a ride as well so I guess the non rebound adjustable should be fine.  Next build will be solo seat more for me I can always the better option then.

[Terry in Australia]

I'd spend the money on the Ikon's Tim, nothing wrong with Hagon's but the Ikon's are infinitely rebuildable and the adjustable rebound is a great way to set them up for our bumpy Aussie roads. As I said, nothing wrong with Hagons, but the Ikons are better.

I made the mistake of buying Progressive 440's for my Triumph Rocket III and wish I'd bought Ikon's, which were cheaper. Cheers, Terry.  

[timbo750]

Well I have come to a point where a decision needs to made. This build was supposed to be mild but with more capacity.  However every turn there seems to be something else that I need to upgrade.

I always had another engine in waiting which was for the next build after I learnt a thing or two on this build. The issue now is budget as so many people can understand so I am contemplating a change in my build strategy.

The other engine is almost complete, it turns over with the kick starter but will need partly dismantling to ensure its condition is acceptable for reliable riding.

This bike was only supposed to be casual 2up riding and the next build just for me with more performance.

I have had many cost blow outs due to unforseen things (I have my third set of fork lowers in postage now)  and a lack of experience that caused things to move slowly and now cause me to change focus. In the end I think I will still get what I was first aiming for but just with a different engine in each frame.

[timbo750]

Started to inspect the other engine. Some stupid PO has used silicone in all sorts of places, the rocker cover for starters and under the cam turret - why? Also looks like it has been used between the cases, but everything seems to be in working order that is there, no points or alternator under the cover but I do have them in a bag. Not sure if the cam is stock or not, I will post photos when I get them of the phone.

Started putting things on the frame and will be send guards and associated bits to get red-chromed, I just hope the pitting is not too bad.

[Terry in Australia]

G'Day Tim, I blew up my first K1 engine in 1981 because the "mechanic" who did some work on it cheaped out and used silicon instead of new gaskets.

What happens of course is the silicon balls up, travels around the oilways and eventually blocks the tiny oilways under the cam towers and the top end, starved of oil, cannibalises itself. I had to do my first ever end rebuild which entailed oversize pistons, new cam towers and new cam, back in the day when I could buy them new over the counter at Maurie Quincey's. Actually I used an Andrews cam rather than the OEM cam, (because it was cheaper) and it was a much sweeter engine for it.

If I was you, I'd drop the sump pan, pull the oil pump and oil filter to check to see if there's silicon in either. If not, it's probably all good, so carefully remove any remains of silicon from the engine's mating surfaces, re-torque the head, replace the rubber "pucks" under the cam, and put it all back together, fill it with fresh oil (just cheap stuff, because you should dump it after the first ride anyway) fit a new filter, shove it back in your frame, and take it for a ride.

It really pays to err on the side of caution Tim, so after an hour or so's ride, dump the oil and filter, check the oil for swarf, silicon bits etc, and fill with new oil and a new filter, and all going well, it should last you another 40 years. Cheers, Terry.