Topic: The latest addition: 1975 CB750 for $300

[ekpent]

Now that everybody has come to grips with the wonderful deal and got the frame all sorted and figuired out I think I would look towards the engine before I got to involved with all the other repairs as it does have 75,000 + miles on it tugging around a Vetter etc. at one time. Luckily its an original owner bike but it is getting up towards the upper end of its comfortable zone maybe. I would get it running well and give the engine a real good evaluation as I moved forward first.May be a 100,000 miler,but thats only 25 away.  Did the owner keep any service records ?

[grcamna2]

Wise decision on the pipes.   Many of the 400 fours rusted in the same spot-they usually fall over and damage the bike when it rusts all the way through. Spotting in another frame section would be the best bet, a good welder should be able to do that so one would never know it was repaired...Larry

I recommend that when you get to the point of welding in the new donor,solid frame piece, install the motor & torque all the other motor mounts down & then tack weld the new frame piece in, remove the motor & then finish weld it so that it will be well aligned w/ all the other tubes & mounts...but I'm sure you most likely already know that. I hope you really enjoy this nice frame restoration !

[MoMo]

Jack,, from Montgomeryville Cycle you say. I worked at Riff's then, when Riff's and Montgomeryville were two of the largest Honda dealers on the east coast-hard to imagine as the two were fairly close to each other. Worked at Riff's through the 70's then Montgomeryville in the early 80's.  Both were good places to work and paid very well...Larry

[mrjack55]

If not for the other signs of excellent maintained cosmetic appeal I might wonder if the bike saw a pond or lake up close or a flooded garage.  I would not drive the bike with that frame.

One way to assess the soundness is to hand the frame to an aircraft structural shop that has as part of its business, airframe soundness.  I don't know if they x-ray them or how they do that but they have equiptment to find out when metal has been compromised beyond safe levels.  For a $300 purchase it is probably not economical for that type of testing.

Even if you skip the professional metal integrity testing and cutout and 'sister' on new frame tube sections I would not ride it at speed.  That is some serious oxidation there. 

In California there's a law requiring the recording of any vehicle that saw water.  Don't know if you have that type of law in your parts.  To me that frame looks like it was submerged.  Looks scary for doing 75mph next to a tractor/trailer semi and the freeway has potholes here and there.

EDIT Just want to add, sorry, do not mean to be a downer! I still think you have made a great deal, you can often get frames for around $100 or so, but I would *only* buy one locally so you can inspect it in person.  When I looked at the pictures I thought there is almost no chance that wall thickness is 'fine' just beyond the visible holes in the tubing, on the contrary the tubing wall thickness is iffy all around the broken through areas and not worth the risk to repair, the problem might come down to 'how much of the old tubing do I need to cut out to have a safe repair for this bike's top speed' someone down the road might buy it from you and you yourself need to feel safe, again sorry if I came off being a downer didn't mean to.

No worries, I appreciate your concern for my safety.    I know a thing or two about rust, I used to build rock crawler Jeeps.  You want to see some rust, look at the frame of any old CJ.  I know that there is always more that you can't see.  I don't need any fancy piece of technology for that.  I have a lead on a decent 75 frame that will play a roll in this story one way or another. 

Now that everybody has come to grips with the wonderful deal and got the frame all sorted and figuired out I think I would look towards the engine before I got to involved with all the other repairs as it does have 75,000 + miles on it tugging around a Vetter etc. at one time. Luckily its an original owner bike but it is getting up towards the upper end of its comfortable zone maybe. I would get it running well and give the engine a real good evaluation as I moved forward first.May be a 100,000 miler,but thats only 25 away.  Did the owner keep any service records ?

Truer words have never been spoken.  He did not pass along any service records.  I know that in the past he has used Castrol GTX motor oil in it.  It wasn't till recently that he switched to Honda motorcycle oil.  Not good, I know.  It needs work, that goes without saying.  It did run today, but it wasn't great.  I never said she was road ready today.

Wise decision on the pipes.   Many of the 400 fours rusted in the same spot-they usually fall over and damage the bike when it rusts all the way through. Spotting in another frame section would be the best bet, a good welder should be able to do that so one would never know it was repaired...Larry

I recommend that when you get to the point of welding in the new donor,solid frame piece, install the motor & torque all the other motor mounts down & then tack weld the new frame piece in, remove the motor & then finish weld it so that it will be well aligned w/ all the other tubes & mounts...but I'm sure you most likely already know that. I hope you really enjoy this nice frame restoration !

Good thinking, thanks for the tip.  If I go the welding route, I'll keep this in mind.

[ekpent]

I will say though that I bought a 1972 that had been in an accident and unfortunately had broke the upper and lower case around the points cover severely. Bought it for the minty bodywork,Lester's,stock pipes etc and it had over 70,000 miles on it.  Must say that when I scrapped the engine out everything inside looked very good and am sure that it still had many more carefree miles left in it.All in how they were cared for and ridden.    Got an extra big bore engine in it now I had laying around 

[MoMo]

If interested a friend has a 750 frame for $40 not all that far from you-Langhorne. PM me if you have any interest and I'll send you his phone number or email...Larry

[mrjack55]

Thanks Larry, that's good to know.  I'm going to look at one tomorrow.  It's a 75 frame that another forum has available. 
If it doesn't work out I'll let you know. 

[mrjack55]

$30 donor fame has been acquired. 

[FuZZie]

$30 donor fame has been acquired. 

Nice!

[mrbreeze]

Like already said.............hella great deal. The pipe and gas tank alone are worth the $300 you paid. I don't think I've ever seen a frame rusted through like that. It had to have spent some time submerged. The 341's couldn't have possibly been original to that bike. My 75' K from Wyoming doesn't have rust on the frame but the left side 341's were blown out worse than your frame. Great deal on the $30 frame. Since the motor will be out anyways...........great time for a powdercoat job (my opinion!!). Whatever you do with it...enjoy!!!!

[mrjack55]

The 341's are the original set, and they are mint!  They were on the cycle for about a year before the PO swapped them out for the Jardine 4-1 you see in the pics.  He placed them in the attic, and they sat there for all this time.  As for the rusted frame, who knows why?  This was his daily driver for 30+ years.  It saw it's share of rain, that's for sure.  Could be moisture build up in the frame.  This part of PA get's very humid in the summer.  There's always lots of moisture in the air in the spring and fall.  If this bike was ever submerged, there would be other signs.  The rest of the frame is solid, very little surface rust.  Even around the Jardine, the frame is in great shape.  In fact, the Jardine it's self is in pretty good condition.  You would think that thing would have fallen apart years ago.

[grcamna2]

I look forward to seeing how you repair it...a great project to learn from.

[MoMo]

I picked this up from mrjack55 a couple weeks ago and finallygot around to working on it. First, off, I pulled the carbs and found 1&2 to have blocked pilot and midrange jets.Bike ran on all four cylinders so I test rode it. When you see the photos below you may call me stupid  but I needed to see how wellthe bike ran considering it has almost 75000 miles.Well, it runs very well and I do love the sound of the Jardine header . I ran it up to 65(my age} then took my hands off the bars and let the throttle snap back. No wobble or shimmy, which is hard to believe considering the condition of the frame.  Check these photos










I removed a half cup of rust from the frame curve between the swing arm and sidestand.  It is my theory that the bike was ridden year round and that water came in the little opening at the swing arm gusset, built up inside the frame rail and rotted the frame from the inside out. Also, the original owner(who seemed to be very meticulous as the bike is immaculate other than the frame) may have used a pressure washer and that also went in the little opening. There isn't any escape once water goes in, see blocked in area in below photo




All for now, have to go work on the donor frame, which will wind up having the same serial number as the original frame...Larry

[ekpent]

That is a weird rust out on that frame Larry.Could see it more plausable if it was a real junker that had been stored outside for years etc,but as you mentioned it was kept up quite well. I do not like to use car or pressure washers on my bikes as that does seem to force water into areas where it should not go and possibly cause other damage.  Might be a good lesson to see and know.  Thanks for the update on that bikes future,and will live again         Eric

[MoMo]

Eric,   it will live again in the donor frame that I got with the bike. Weird that the donor frame was built the same month and the serial numbers are only 720 off.  Jack was going to bring the bike back to original but too much has been changed(paint, seat, fork ears) to make it worthwhile.  If it were a 71 I'd consider it but the cost of those items would not make it feasible.  Does anyone think I should start a new thread or continue the saga here?...Larry

[70cbk0]

wow, deal of the year!

[Terry in Australia]

I do not like to use car or pressure washers on my bikes as that does seem to force water into areas where it should not go and possibly cause other damage. 

+1 Eric, Back in the 1990's I used a pressure washer on my BMW R100RS to remove the brake dust from the cast iron discs, anyway, after one "spirited" ride the front end felt kind of weird, so I put it up on the centre stand and spun the front wheel, and there was all sorts of side play and a "crunchy" noise. I pulled the front wheel and axle and the wheel bearings literally fell out! They didn't resemble wheel bearings any more though, they were just shapeless brown slugs.

I rebuilt the (very expensive) rear suspension linkages on my neighbours Suzuki RM250 Motocrosser a little while later, once again, all the bearings were all shot, and he told me that he couldn't understand why, because he pressure washed his bike after every outing? Ha ha, that was the last time he used it........... Cheers, Terry.  

[Stev-o]

Lar - the title fits, but it's not in the project bike thread, so you may want to have it moved?

It is very odd how it rusted, almost looks like acid damage? Good luck, we'll be watching.

[Terry in Australia]

All for now, have to go work on the donor frame, which will wind up having the same serial number as the original frame...Larry

Excellent pics Larry, and that really is scary mate. How are you going to modify the serial numbers? Cheers, Terry.

[MoMo]

Thanks for the compliment, Terry.  I am  going to fill in the two digits that do not match and restamp them with the titled frame numbers.  If the type style does not match, I am going to grind the serial number away and restamp the titled number.  The ID plate will be removed and the titled plate installed. But I did not say that    I plan on doing a title trace on the donor frame, and also let any buyer know that the frame was changed.

I still cannot get over the damage, I bought a CB450 that had been submerged for a while that did not have any damage. There is a little drain hole in the cross member that may have been plugged on the 750 and if the PO rode all year round water would fill the frame if the hole was plugged...Larry

[Terry in Australia]

No worries Larry, and I don't imagine you'll have any problems. Over here we have a real problem with cars being "rebirthed" where someone will buy a smashed car with a title (usually from a private seller who's insurance lapsed prior to the crash) then steal a similar car and swap the engine and ID plate etc from the crashed car to the stolen car. Much harder now than "back in the day", but still do-able if the thief is a good fabricator.

Sometimes engine blocks were restamped, but the cops could get them XRayed and this would reveal the old numbers. The trick apparently was to grind off the old numbers then ARC or MIG weld over the area, and grind it flush, then restamp it, because the welding process penetrated the metal deep enough to obliterate any evidence of the old numbers. I've never tried it myself but the guy who told me was a career criminal, and was a wealth of knowledge when it came to breaking the law. Cheers, Terry.  

[ekpent]

Might as well just start a new build thread in the project area Larry with a short history of how you acquired it.She's yours now.

[MoMo]

Eric,   You're the second to say that so I will start anew over there.    I picked up a spare low mileage motor today even though the 75000 motor runs very well...Larry

[mrjack55]

Holy crap, you rode that thing?   You are indeed crazy.

I'm glad you got a hold of that project. It needs the hands of a master.  Looks to be a little out of my league.
I'll keep an eye out for your new build thread so I can subscribe. 

[MoMo]

Holy crap, you rode that thing?   You are indeed crazy.

I'm glad you got a hold of that project. It needs the hands of a master.  Looks to be a little out of my league.
I'll keep an eye out for your new build thread so I can subscribe. 

Jack,  it is scary looking but the motor serves as structural support between the rotted sections.  The dangerous part was the rusted swing arm gusset, which I thorought tapped to make sure it was secure enough to ride my 5 mile initial test rode.  Bike is completely apart as of now, I will start the build thread when I get a working camera...Larry