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Discussion Starter #1
Hi all,

Well, if there's some good to come out of this Coronavirus ordeal; I've dusted of my forgotten CL450K1 project! The bike is already torn down, and I disassembled most of the motor last night. Overall first impression is that the internals look pretty good. Going to be checking the tolerances on the top end shortly, but I expect it's in decent shape.

My goal is to avoid permanently modifying any of the original parts, but not necessarily to put it back together completely as original. I'd like to rebuild the engine and powder coat the frame parts, and then see what happens from there.

My first question (of likely many) is where to source a rebuild kit?
The ones over at 4into1 seem reasonably priced: Engine Rebuild Kit w/ Pistons - Honda CB450K CL450K
And then there's one at Common Motor, albeit a bit pricier: Honda CB450 / CL450 / CB500T Engine Overhaul Bundle | Common Motor Collective

My second question is it worth it to overbore slightly while I've got it apart? I don't plan to heavily modify the engine, but while I'm in there, I might as well consider what I can do to reasonable improve the performance. I also saw these: Pistons For CB/CL 450's (Pair) - Charlie's Place

This will be my first complete rebuild, so I'd love to hear from others who've done so with the 450, and what their experience was like!

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Well, the first thing I notice is you took the head apart before breaking the cam chain at the master link and removing the head, then rotating the cams manually until all valves were closed to remove any tension from the camshafts so the cam bearings can come off freely. As for the overhaul kit, "a bit pricier" is not an accurate description, almost double would be more accurate and for the difference you get allen bolts for the engine and some Hondabond... hmmm.
You need to first determine the condition of your cylinders and pistons according to the FSM specs before ordering. As for overbore, if you're just going to ride the bike like most people do, there's not enough gain in going larger on the displacement to make it worth the money. And please tell me you didn't watch (or buy into) the CMC video of a 450 teardown...
 

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Discussion Starter #3
Hi Tom,

Ha, yeah. Realized my mistake pretty quickly. Broke the chain after and was able to continue with the job. I'm down to removing the clutch & rotor and then splitting the bottom now. Also, noted on the price - I was being more polite than my actual thoughts were about the difference.

I've watched that and other videos as well, but if there's definitive guide out there you recommend, I'm all ears and eyes.
 

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Your best bet is to read the FSM and ask here. I personally wouldn't trust any videos on this engine because there are few, if any, people making these videos who actually worked on these engines in Honda shops when they were being sold and were current bikes... but you have many people here who fit that description. When in the slightest doubt, take the time to post the question in this thread. I'll be watching it as will lots of others, and I'm on here every single day, often many hours of each day. Depending on how many miles were on the engine, I'd suggest replacing the cam chain - and here is the best chain (OEM) at the best price
 

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Discussion Starter #5
Thanks! I generally take most videos with a grain of salt as well; sometimes just nice for the visual reference.

Appreciate the link - I'll definitely grab a new one. My goal is to reuse what makes sense, but if it's more beneficial to just replace for the long haul, I'm good with that too. Don't want to cut any corners if I can help it.
 

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Find a machinist - he'll evaluate the cylinders and tell you if and how much you need to overbore in order to clean things up. The cylinder taper spec on these engines is ridiculously low.
Only then should you order new pistons/rings - you'll need to have them in hand before he can proceed with the bore job, as he will bore to match them precisely.
 

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Discussion Starter #8
Found my first real issue during the tear down; the casing "tab" where the kick start spindle rests seem to have broken off. There seems to be a hairline crack around where the tab meets the casing too. Should I go ahead and start looking for a replacement case? Is this a common issue?
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I wouldn't say it's a common issue, probably only with owners who allow the kickstart lever to fly back to the stop on its own. Repeated slamming against the stop would crack it I'm sure, but I've never personally seen one cracked, only pictures of the problem since I've been here. The 5 speed engine lower cases are all the same AFAIK. I have a spare if you can't find one
 

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Discussion Starter #10
I wouldn't say it's a common issue, probably only with owners who allow the kickstart lever to fly back to the stop on its own. Repeated slamming against the stop would crack it I'm sure, but I've never personally seen one cracked, only pictures of the problem since I've been here. The 5 speed engine lower cases are all the same AFAIK. I have a spare if you can't find one
Thanks! I remember the PO mentioning the kick having an issue; the pedal was removed when I bought it, so I've only used the electric start. Waiting on the clutch/filter spanner socket to get here so I can dig into the bottom end and inspect.
 

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My second question is it worth it to overbore slightly while I've got it apart? I don't plan to heavily modify the engine, but while I'm in there, I might as well consider what I can do to reasonable improve the performance. I also saw these: Pistons For CB/CL 450's (Pair) - Charlie's Place
I found these after market pistons (and all the other bits) for $80 from Japan
I re-bored the cylinders to +1.0 at a local shop ($60) and they worked great.
I ordered another set for my CB175. I suspect that it will take longer to get delivered due Covid slowing the borders. It took a week last time.
 

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Found my first real issue during the tear down; the casing "tab" where the kick start spindle rests seem to have broken off. There seems to be a hairline crack around where the tab meets the casing too. Should I go ahead and start looking for a replacement case? Is this a common issue? View attachment 308829

It's not common but not exactly unheard of either.

I had a similar issue in my CB500T engine. In my case the tab didn't actually break off per se but there was a groove that got worn completely through and allowing the kick starter shaft to spin 360 degrees all the way through.

A few options to fix this.

1. Find a replacement case
2. Have a welder add more material (aluminum) back to the tab
3. Or in my case I fixed it by making a small steel plate from a L bracket then drilled/tapped a small hole and bolted that plate on. For further reinforcement I also used JB Weld underneath said steel plate just make sure everything is tight and secured.
 

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Discussion Starter #15
Thanks for the help fellas. @76TWIN, that repair looks great - I think I may go that route if possible.

For the cylinders; I'm considering these options:
1. If it's within spec; I could just done a hone job, reuse pistons and install new rings.
2. Bore between .25mm (1st oversize) and 1.00mm (4th oversize). Seems like this range is fine with the stock sleeves? Best quality piston kit available?

Plan is to take the head to a friend to have them inspect and do a valve job (assuming it's needed).
I've read that the intake valve guide bosses can be trimmed (Hondaman)...
I'm assuming that's what the below is offering as well. Anyone know who they are?

Others items of interest while I have it apart:
1. Milling the head .010"
2. Torsion bar spline modification
3. Shaving the flywheel/rotor

For reference, there's a copy of an old post by Mark Paris here I was reading in regards to engine tuning:

Ignition work:
I'll be replacing the ignition coils for sure, and was considering going with an electronic points replacement.
Any other mods to consider? I'll likely build a new wiring harness while I'm at it.

Suspension... TBD.
Looks like I could gain a little more travel/height by doing a CB360 swing arm swap, and maybe lengthening the forks to match.
 

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Suspension... TBD.
Looks like I could gain a little more travel/height by doing a CB360 swing arm swap, and maybe lengthening the forks to match.
Using the longer 360 swing-arm LOWERS the back end........
It also requires machining the 360 arm to fit and provide adjustment for the larger diameter 450 axle....
Gaining travel and height is better served by using longer shocks (front, rear, or both), although lifting the engine will change the center of gravity, and depending on how well fore/aft lift is matched, possibly weight bias, rake, and trail.......

Several of the engine mods you mentioned are unsuitable and/or unnecessary for a streetable bike...... JMHO
 

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For reference, there's a copy of an old post by Mark Paris here I was reading in regards to engine tuning:
Where to start...?
If you plan to do any of this stuff, then have at it - but don't expect anyone knowledgeable here to give you 450 advice in the future. I don't mean to be blunt, but if there was a way to take this guy's BS off the internet, it should be done.

NOTE: THE FOLLOWING IS NOT RECOMMENDED, IT IS INTERNET LORE

#2. The intake valve rockers wore badly. This was from folks running too light oil (cheap 10w40 or 10w30), and running it too long. The recommended change interval is 750 miles or less, because the top end really beats up the oil. Use 20w50 if you don't mind losing about 1 HP. Use Castrol or Torco, in any case, because it survives these hot-running engines better than almost anything but synthetics. Don't use synthetics, or you might lose your clutch. When starting it hot, WAIT 45 SECONDS BEFORE DRIVING, because it takes that long for the oil to reach the intake rockers on hot startup (honest!). If your lifters are worn, get new ones. They can be replaced through the adjustment cap holes. Set the intakes at .003" and the exhausts at .004" (I know the manual says .002" and .003", but that's for quiet, not for longevity). Worn lifters both clatter and reduce the lift a lot, as much as .100". Worst case, they also damage the cams. Look inside with a flashlight for score marks. They can be resurfaced or replaced fairly easily.

#5. 450 Hop-ups:

After you've replaced those worn lifters and cleaned up the cam, give it a nice valve job to make it seal well, bore it .25mm (1st oversize) to gain almost 2 HP, mill the head .010" and remove the resulting sharp edge around the bore, trim the valve guide bosses on the intakes (they are too big), reassemble and set the timing an extra 2 degrees advanced. Grind off an extra spline on each torsion bar (for the valves) and reinstall 1 notch "extra" tight. This will let you spin 10,500 RPM safely, and it will, very willingly.

END OF INTERNET LORE

Now, the truth:
the exhaust followers wear far more quickly than the intakes do under normal circumstances and proper oil flow. As for startups, if you listen to what he said you would believe that cold starts are completely fine but hot restarts are when you need to wait for oil flow. The reverse is actually true, it takes up to two full minutes to get oil to the top end so you can safely ride away without causing excess wear when cold, hot restarts aren't really a problem. As for valve settings, he clearly never read the manual - all valves are set (according to factory specs) at .0012" but we commonly set them at .002" intake and exhaust since even a .0015" feeler is difficult to work with in between the follower and cam lobe. Not sure what he means when he says "lifters" unless he's changing terminology midstream, as the 450 top end uses followers. Yes, you CAN change followers through the valve covers BUT ONLY IF YOU THOROUGHLY UNDERSTAND THE ENGINE DESIGN AND HOW TO DO IT PROPERLY. First oversize bore job (0.25mm) will give it almost 2 additional horsepower? By that logic, my 450 (bored to S16, 4mm oversize) should get 32 more horsepower! Right. I personally wouldn't mill the head unless it was absolutely necessary, and cleaning up the intake ports will help any engine but it's not likely you'll feel any difference if that's all you do. And as far as setting the timing an extra 2 degrees advanced – if he's talking about cam timing, I'd love to know how he accomplished that because all you can do is move it one tooth at a time since the sprockets are not adjustable. And finally, grinding off a spline on the torsion bars is a disaster waiting to happen. It roughly triples the amount of preload, and torsion bars can only twist just so far before they break. If you want to spin 10,500 RPM and actually make more horsepower while doing it, get a set of camshafts from MegaCycle. If you need an example, look at the drag strip run in my signature.
 

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Discussion Starter #18
Thanks guys; if you don't ask you don't know I suppose! Given that info, I'll revise my goals a little!

My primary goal is to get a good quality top-end job done. I'm not chasing HP, but if I've got the thing in pieces, and access to a good machinist, I figure I might as well investigate what can safely be done to improve performance, however minor it may be. Sometimes just the process alone is worth it when you enjoy the work (but of course, best bang for your buck advice is always welcome).

So no torsion bar modification, use manual for all service specs. Check.

Suspension clarification:
@66Sprint When I said I was looking into the 360 arm, I should have clarified I would indeed be using a longer shock in that case. I'm aware of the geometry changes and would be working with a friend who's a bit of a suspension guru (I'm not by any means). The goal here would be to gain a little height & travel to make it a little better adjusted off the pavement - think gravel/forest service roads.

@ancientdad, sounds like the megacams can be worthwhile? I don't have any inclination to switch to a valve spring setup or a race setup, but I see they offer jobs that are compatible with the stock setup...

If decide to bore between 1st and 4th (be it for .2 or 2 HP!), can anyone recommend a particular oversize kit?
Are any of the piston & ring sets better than OEM? Any of them garbage?
Can you use the stock pistons with an OEM oversize ring set?
I've even seen NOS Honda kits +1 on ebay...
 

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MegaCycle has a couple of grinds that are safe to run with stock torsion bars but only the 120-00 set is okay with stock pistons. I'm running the 120-40 set with 74mm 11.6:1 pistons and the trade-off is giving up some low end power in exchange for a significant increase above 6000 all the way to 10,500-11,000. If you're thinking light off-road riding, you'll want the torque that comes with either the stock cams or the 120-00 set. If you were to bore it to 1mm oversize and had a machinist fly-cut the pistons .060" (for valve clearance) you could run the 120-x11/x12 set. I had a set of them early in my red bike build and it ran nice, but it wasn't the powerband and overall increase I was looking for so I swapped cams with an HT member for the 120-40 set I have now, but with those it's fairly flat under 5000 rpm so it makes riding a bit different as you have to compensate for the lack of torque at low speeds.

You could run these with the 120-00 cams and likely get a broad range increase you could feel. You'd need 2 sets as for whatever reason they price them per piston. If you go that route you'd need to make sure the machinist knows they're forged, as the clearance is different when using forged vs cast. Total dollars you'd be spending for the cams and pistons would be around $700 to $800
BTW, here's the cams available from MegaCycle
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And as further reinforcement of one of my earlier points, there's this to consider (if you haven't seen it yet)
 
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