Project CB690 (KTM 690 engine in a CB550f frame)

[goodoltup]

Finished welding the patch, and welded in the fan switch bung. My intention was to use the original 690 fan switch, but I bought the wrong bung thread size. So I took the opportunity to buy a new, lower temp switch. People on forums say that the 690s run hot, and I'm not looking for any trouble with this new radiator, as it will be flowing in a different direction and just behaving differently. The new switch operates at 87C, instead of 102C.

 

[goodoltup]

Welded in the bottom pipe and test fit.

 

[goodoltup]

Marked out and installed the upper pipe and test fit.

 

[goodoltup]

I wanted to use the 690 cap because it is a small diameter and looks pretty good, so I chopped it out of the 690 radiator. I drilled a hole in the top of the radiator with a step drill and welded the cap on. This wasn't as hard as I thought it was going to be actually.

 

[goodoltup]

Almost done with the radiator! I've been pressure testing it the whole way with soap and water and only found one pinhole leak, which I repaired by reflowing the area around it. It is pretty forgiving as far as sealing goes. Bear in mind I've only been welding aluminium for a week or two, and I readily admit I am not good. But this is working and has saved me hundreds of pounds of custom radiator manufacture, and has been pretty fun.
Next I need to weld bosses on the sides of the radiator to hold some guards/beauty panels, more on that later.

 

[Sderbyshire]

Fabulous work, bravo!

 

[goodoltup]

Thank you Sderbyshire!
I've skipped a bunch here, but the radiator is finished. It looks great, if you imagine it with the front guard and side covers. I took it for a few rides and it works great.
Now, the bike is ready for teardown. Next updates and pictures should show a pile of parts!

 

[Popeye SXM]

Great bike. I like the new rad

 

[Maritime]

Once you black that rad out it will basically disappear. Looks great.

 

[doc_rot]

nice work on that radiator!

 

[Jimbonaut]

I can only imagine what this bike must be like to ride. KTM engines are awesome so this must be an absolute blast when you give it the beans

 

[goodoltup]

Thank you all!
It is shocking to ride. It has a top-end rush, but really pulls everywhere in the rev range. Maybe because of the added wheelbase, but it doesn't really want to wheelie, so all the power goes into pushing you forward, and it just pushes and pushes. I like to take big handfuls and short shift it, that's really fun. Only problem is that it is kind of chug-a-lug if you're not careful, and riding around town can be a chore because of that. It is not civilised. The power is savage. I love it.

I've counted about 12 weekends of work to get the bike completely finished, IF if worked every weekend (which I won't) it would be three months. I'd say more like six months. Which is bang in the middle of winter. I think instead of taking it apart I will keep it on the road and enjoy a little, and have it completely finished aiming for next spring.

 

[Maritime]

Thank you all!
It is shocking to ride. It has a top-end rush, but really pulls everywhere in the rev range. Maybe because of the added wheelbase, but it doesn't really want to wheelie, so all the power goes into pushing you forward, and it just pushes and pushes. I like to take big handfuls and short shift it, that's really fun. Only problem is that it is kind of chug-a-lug if you're not careful, and riding around town can be a chore because of that. It is not civilised. The power is savage. I love it.

I've counted about 12 weekends of work to get the bike completely finished, IF if worked every weekend (which I won't) it would be three months. I'd say more like six months. Which is bang in the middle of winter. I think instead of taking it apart I will keep it on the road and enjoy a little, and have it completely finished aiming for next spring.

good plan, functional is fine for now, pretty can come over the weeks/months you can't ride

 

[Jimbonaut]

Savage sounds about right. What little I know of KTM's that's as good a description as any. My mate's 950sm is an absolute reprobate when cajoled, and it doesn't take much cajoling that's for sure. There's a guy local to me who's an old KLR guy and keeps eyeballing my C model - he just bought a new 690 Enduro and wants to swap bikes for the day. He won't have to ask me twice

 

[goodoltup]

Small diversion, I removed the up-and-over type garage door and replaced it with a side hinged door. Not completely done yet, it still needs some brick work and final levelling.

 

[CarbsAndCylinders]

Small diversion, I removed the up-and-over type garage door and replaced it with a side hinged door. Not completely done yet, it still needs some brick work and final levelling.

I like those types of doors, yours look pretty cool.

 

[goodoltup]

The KTM, as purchased, had been remapped at some point. It had a free-flowing exhaust, no changes to the airbox or filter, and the O2 sensor didn't seem to work. So who knows what map was loaded in the ECU. I've found the bike snatchy on the low end, and surgey on low rpm steady throttle.
I got TuneECU and a cable, watched a YouTube video, and loaded a map. Just to see if really worked, I loaded a pretty extreme map, the stock restricted HP version that some bikes came with originally. It is around 33 hp as opposed to 63 hp unrestricted. I figured I could tell the difference easily, and then could move on to using other custom maps or modifying an existing map for my purposes. It all went well, and the map was loaded and I went for a test ride. I actually really liked it! It's not so violent, and more manageable in town. Much more tame. I probably won't leave it like this, but it's good to know.
Maybe I could get an ECU and harness for an Enduro model, they have a switch to engage 3 different maps. I could have a low hp one, and some full power ones. A switch on the handlebars could be added. Worth considering!

 

[goodoltup]

I'm considering shortening the swingarm 95mm to correct the long wheelbase. Below is a jig that I would have laser cut to keep everything true. The brackets in the back have two sets of holes 95mm apart, so I can take the stock swingarm and get it all set up and weld the brackets, then cut a section out of the swingarm and move the end to the other set of holes. The brackets with the slots are for the shock mounts, which need to stay in the same spot. The slots are to allow for some up and down movement of the shock mount blocks since the swingarm has a small taper to it. I will just get two more shock mount blocks machined from the previously used design.

Still enjoying the map from the above post, though I may put it back to full power soon. For now, it really makes the bike a lot more rideable in town which is very welcome.

 

[goodoltup]

Ok here we go on the swingarm shortening. Not entirely sure this will work. Below is an eBay purchased swingarm, same model and year as the one installed on the bike. I cleaned it up and cut the shock mount off of the bottom, just like I did last time. I'll clean it up better after I know if it will work.

 

[goodoltup]

These are the laser cut parts I received. I'm very happy with the service, quality, and cost. It was around £160 delivered. I could have made the parts out of scrap for almost nothing, but this was more fun. I can also keep the base to act as a swingarm jig for future projects.
Note the rectangle bits with the four holes on the baseplate, that will come later. Also note that they are bent. On this occasion it doesn't matter, but maybe their packaging needs improving. Also note I got 4x each of the sub parts, it was only a few extra pounds to get the extras so why not, they can always be used for other projects.