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Old 11-22-2013, 05:27 PM   #31
Leaf
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Originally Posted by Azazel View Post
Thanks Leaf, that's very kind of you. I called a few shops and they basically acted like I was retarded for asking about a valve inspection on a head that's already off the engine, so I guess I'm going all-in on a bedroom rebuild here.
Nice.

When I was a kid, I remember dumping a box containing a torn apart XR200 engine (with one of the valves embedded into the top of the piston) into the arms of the Friendly Local Motorcycle Mechanic and saying "fix please!" The look on his face was Mastercard-priceless.

But rebuilding motorcycle engines is fun! Don't be scared! Get the tools you don't have inexpensively off Horrible Fright, er Harbor Freight, and just doooo eeeet.

And, pikshurs, please!

Maybe we could rebuild both our motors at the same time, share photos and grumblings, and have friendly competitions of oneupmanship over whose motor is more screwed... I have that CM400E motor that needs looked into... But I wanted to do a CB900 first... Ohh decisions...
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Old 11-22-2013, 05:59 PM   #32
WYO George
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If you run into a snag on the engine let me know. I have a complete factory service manual for my '78 and while the two aren't 100% the same bike, they should be the same engines and I'll gladly look up info if you need it.

George
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Old 11-23-2013, 09:58 AM   #33
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Thanks George! I've got both sitting beside me, so it's just between me and my shaky hands at this point.

New tank! Off a CB450 this time, so I've gained an extra liter of fuel capacity over my previous one. Going to swap the handlebars out to prevent this one from getting punched in if the bike topples over.

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Old 11-23-2013, 10:37 AM   #34
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Extra capacity is good!! I'll be cutting and welding my stock tank for some extra capacity. It has a dent right on one of the style lines so it's no waste to cut it up. I'm thinking I'll shoot for 4.5-5 gallons total. Maybe I'll get off my butt and start working on it in a couple weeks. You've inspired me to do a build thread!
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Old 11-29-2013, 03:17 PM   #35
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Recently I've been reviewing my goals and become concerned at the longevity of the frame I've chosen to work with here.
(Picture grabbed from another build forum, not mine):



Primarily my concerns are:
- That the crankcase acts as the base portion of the frame, rather than bottom tubes.

- The center downtube is a hollow cube of 1/4" steel halves, welded in the center, which flares out at the bottom where the crankcase bolts on.

- The tail is made up of two thin leaves welded onto the arches of secondary loops.

Overall I'm wondering at the longterm survival of this in rough terrain, especially with any meaningful fuel hanging off those funky tail supports.


In other news, cylinder head is in a friendly machine shop being looked at, should know if it's salvageable next week.
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Old 11-29-2013, 06:27 PM   #36
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Mine has been fine over some really rough stuff, and with that sidecar bolted onto it yet. I don't think the engine-as-stressed-member is a weakness at all. I have broken the upper rear sidecar mount a couple of times, but the actual load-bearing part of the motorcycle frame has taken it all like a champ.

I think your biggest hurdle to off-roading it is the short travel of the stock suspension, especially the rear. It likes to bottom out on really rough stuff and make my back sore. Perhaps without a sidecar on it, yours won't be so bad. But mine is a back breaker if you're not standing on the pegs. You may want to see if you can devise some way to put some longer travel shocks on it. Which may be somewhat difficult, seeing as how the CB400T's double-clevis shocks are of an uncommon configuration...

The other thing that is a little annoying is that big ol fat exhaust collector / crossover chamber right under the engine. It likes to hang up on rocks. At some point, I have a CL360 exhaust that I want to try to fit on mine to try to get all that stuff up off the ground where it's hitting stuff, but that will require moving the electronics, and that is annoying. Not really feasible to just remove the collector either, imo, as I believe it's required for proper exhaust scavenging and you'll lose power from the already somewhat anemic engine without it. Though perhaps a crossover pipe of some sort would have the same effect. But then you've got something hanging down there to catch on rocks, again, just not quite as fat a something.

Also, for really heavy off-road, you may want a larger front wheel. I am running an 18" rim, but with the tire on it it's the same diameter as the stock 19" w/tire. It will bounce up over the medium/small obstacles if you give it a little sass, but it doesn't like the big stuff at all. Maybe a dirt bike front wheel would be good if you are going to be really serious, but I don't get that serious on mine. Nothing worse than logging roads for me.

It's also got a pretty tall 1st gear for off-road stuff. On mine, I went up a tooth on the front sprocket to gear the whole thing down a notch, but it's still a little too tall for doing really nutty stuff. And at 65 mph on the highway, it runs really high RPMs and burns more fuel.

I dunno... Just my opinion, all that.

Leaf screwed with this post 11-29-2013 at 06:43 PM
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Old 11-29-2013, 09:22 PM   #37
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Engine as stressed member is one of the best designs of all. Don't sweat it.
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Old 12-07-2013, 12:24 PM   #38
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Soooooo, at the risk of being a nag... How's the project coming?

I'm too busy with my day job to work on my own projects, so I have to get my fix somewhere!
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Old 12-26-2013, 12:40 PM   #39
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Sorry guys, it's been a long cold month so I've spent it acquiring parts and getting stuff fixed.

Cylinders honed, new gaskets & NOS Pistons, valve head re-machined, newly painted in high-temp black and new valve seals:



I just need to acquire piston rings, side cover gaskets, and a ton of assorted o-rings and I'll be ready to put it all back together next month!
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Old 12-26-2013, 01:34 PM   #40
WYO George
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I wouldn't worry about the frame as it's a lot stronger than you're imagining it to be

Engine parts are looking good, keep up the build!
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Old 12-28-2013, 12:59 AM   #41
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Removal of exhaust collector chamber requires carburators rejeting !
But, gives Your bike 10-15 kilos off and ~3 inches of clearance more
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Old 12-29-2013, 03:55 PM   #42
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I think the carbs were already rejetted by the guy who built the bike, because the exhaust is a non-collected aftermarket Mac 2-2 right now and I didn't notice any sluggishness or loss of power when redlining it this summer. Unfortunately the 400-450 series engine can't be jetted properly to run with pods instead of the airbox, because that would shave some serious weight off and allow me to relocate the electronics further inside the frame.

I do need to remove the carbs and give them a cleaning though, no point in gutting the engine and then putting dirty carbs back on it!
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Old 12-29-2013, 10:36 PM   #43
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Unfortunately the 400-450 series engine can't be jetted properly to run with pods instead of the airbox
Who says? Sure they can.

I didn't have a lick of carb problems with Uni's or K&N's on my 1980 400 or my '82 450. Can't remember perfectly so don't quote me, but I think I went up one washer thickness on the needles and to 130 main jets. Again, this was nearly 30 years ago I'm thinking back...

Raced in BOTT (Unlimited Twins) just fine and held my own with many bigger bikes.

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Old 12-29-2013, 10:41 PM   #44
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Interesting position for oil cooler
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Old 12-29-2013, 11:06 PM   #45
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Interesting position for oil cooler
Heh, heh

After burning the valves, melting the pistons on my 400T and rebuilding her, I figured the sump mounted oil cooler-like finned affair on the newer 450T's was a step in the right direction, but not quite enough for me...

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