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Discussion Starter #1
Bought the bike last spring knowing that it had one of the valve's drop and punch a hole in one of the pistons and also breaking the head as well. Ex owner had done quite a bit of bad mods and found this bike at one other forum where he got absolutely trashed for the mods he did, can't find the forum post anymore though.

Bought used cylinder in the original size, new pistons, rings, cylinder head and gaskets. Took the cylinder and head to a local smith which glass bead blasted them, redid valve guides, honed cylinders etc. Rebuilt the upper and found a leak dead middle in the front of the engine between the cylinder and crankcase.

I think a rebuilt the upper engine 3-4 times last summer but I didn't fully get rid of the oil leak. I rushed it, didn't clear the head bolt threads well enough and there was some problems with Athena's gasket sets as well. Gave up and focused on other things since last June but now that I have a garage to work in I'll start on her once again.

The plan is to redo the entire bike part by part.

I have a huge lot of all kinds of parts, old and new. I will be redoing the electrics with motogadget m.unit blue and m.lock (which I already have). New lights, indicators, anti-gravity battery and reg/rec.

The rear of the frame will be cut off and redone to straighten out the lines, stock frame isn't my cup of tea. The exhaust will be redone with stainless and new silencer's and I already have a CB 360 tank that I'll use instead of the stock one.

Brought the bike to my garage last Saturday and stripped it down. Allready stripped the upper engine down, no problems that I could see there. Noticed a bit of vertical play on the crankshaft on one of the pistons so a lower rebuild is mandatory. That was a plan anyways as I have a older cb400t's kickstart assembly waiting to be installed. Also the whole engine will get glass bead blasted and powder coated.

Here's some pics as the bike is atm.
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Puller should be in the mail tomorrow...

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The frame stripped down.

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The inside of the tank is getting treated.

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Old wiring harness is a mess.

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Some of the parts I have.

Posting on my phone so the quality of the posts ain't perfect. Will post later about the engine rebuilding etc.
 

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SOHC scrambler projects are rather rare, looking forward to following your build. Powder coated engines are also a might unusual, like to see how it works out.
 

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Discussion Starter #3
SOHC scrambler projects are rather rare, looking forward to following your build. Powder coated engines are also a might unusual, like to see how it works out.
Decided to go with scrambler as I'm having a hard time finding rearsets/transfer kits to suit a more cafe riding position and the one I've found is 300€+ which seems like too much.

As for the powder coated motor, I want to get an even finish across the motor, if you have any ideas feel free to comment :unsure: at least powder coating should withstand some amount of heat.
 

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Interesting project.
PC on the engine needs to be done very lightly, they can get carried away with doing it and create a nightmare. This is an air cooled engine so it has to release the heat thru the fins.
I just did my CL350 engine with CeraKote, the finish that's applied to guns. Rather expensive way to go but at the same time you can shoot carb cleaner on it to clean it up. Only way to remove it is media blasting.
 

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Discussion Starter #5
Interesting project.
PC on the engine needs to be done very lightly, they can get carried away with doing it and create a nightmare. This is an air cooled engine so it has to release the heat thru the fins.
I just did my CL350 engine with CeraKote, the finish that's applied to guns. Rather expensive way to go but at the same time you can shoot carb cleaner on it to clean it up. Only way to remove it is media blasting.
Might look into getting head and cylinder CeraKote'd and rest PC.
 

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Discussion Starter #6
Didn't have time to work on the bike today but got some time to post about it..

So the upper engine was redone last summer and I rode the bike for like 10km total last summer between upper engine rebuilds. There's still clearly visible honing marks in the cylinder.

Disassembled clutch and oil pump yesterday and found out some "mods" that I didn't enjoy finding.

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Clutch springs were below service limit length and the last owner had just rebuilt the clutch with new plates and took 4 washers, grinded them down to fit them and threw them in... Ordered a set of new as springs which are 10% stiffer than factory ones.

Also while disassembled the oil pump noticed that there was no gasket between the pump and the crankcase. Didn't have a tool to measure the oil pump wear, will check it later.

While I was scrolling eBay for the springs also ordered new timing chain, oil pump drive chain, timing chain guide, oil level sensor and set of 2 cylinder head bolts with the gasket sleeve above threads, no idea if they'll fix my oil leak but I'll give it a shot.

Propably more pics and a post tomorrow.
 

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Discussion Starter #7
So some progress today, took down the entire motor, not too happy about the findings...

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After cracking the cases open found that the top of the oil sump was full of this crap.

Disassembled the motor until I had bare crankcases left. More disappointments to come.

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Crankcase cracked where the transmission is, also marks left by the transmission inside the crankcase but no idea why this has happened.

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Strange marks near the oil pump. Looks more like a casting defect.

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One of the rods had vertical play, bearings are a total bust and the rod has taken quite a bit of heat :eek: shaft seems fine tho.

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Someone took an angle grinder and grinded of a piece from the bottom half of the crankcase... And did a very poor job at it as well.

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And here's the bits and pieces I found inside the lower engine, copper washer which looks like a washer from the head bolts, some black plasticy fibery stuff and some metal bits...

What a piece of work.
 

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I would mic the crankshaft to be sure it's good. Need 1 rod.
Looks like the crack is caused by the bearing locating dowel being crushed into the case, PO didn't align it correctly.
The crankshaft carrier should be fine, odd surface finish in the oil pump area. That part cannot be changed w/o replacing the upper case half. Those 2 pieces are match machined as a single unit.
The black bits in the oil sump pickup aren't bad, they come from the balancer rubber dampeners when the get hard and start breaking up. Replace the balancers with the one piece later version. Here's a partially plugged screen
305624


The lower case half can be changed easily. Want an oil cooler? Just get a CB/CM 450 lower case and you've got it.
You can also add a kickstarter to the engine if wanted.
 

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Discussion Starter #9
I would mic the crankshaft to be sure it's good. Need 1 rod.
Looks like the crack is caused by the bearing locating dowel being crushed into the case, PO didn't align it correctly.
The crankshaft carrier should be fine, odd surface finish in the oil pump area. That part cannot be changed w/o replacing the upper case half. Those 2 pieces are match machined as a single unit.
The black bits in the oil sump pickup aren't bad, they come from the balancer rubber dampeners when the get hard and start breaking up. Replace the balancers with the one piece later version. Here's a partially plugged screen
View attachment 305624

The lower case half can be changed easily. Want an oil cooler? Just get a CB/CM 450 lower case and you've got it.
You can also add a kickstarter to the engine if wanted.
Thanks for the info.

Yeah going to get the crank mic'd by next week most likely. Hoping that I don't need to replace it but most likely will. Wondering if it failed due to oil pump not having a gasket so maybe the oil pressure wasn't ok.

After the crankshaft is mic'd and hopefully ok I'll get a new rod and definitely looking for a 450 lower case if I can find a decent one. I already have the kickstart assembly and seal ready to go.
 

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Discussion Starter #10
IMG_20200326_160151.jpg

IMG_20200326_160159.jpg

Seems like I have the one piece balancers on my engine, makes me wonder why there's so much of this black rubbery stuff on top of the sump...
 

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There is no oil pump gasket on these engines. Most likely cause of the bearing failure is running very low on oil. I'm guessing that it's the left rod that's bad, usually the first one to go.
The only other black rubber/plastic in the engine is the cam chain tensioner blade and the front chain guide.
 

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Discussion Starter #14
Hmmh, at least my service manual show's an gasket between the pump and crankcase as well as my gasket kits do have a gasket for it. Did they change it between the TI and TII hawk's?
 

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The very early engines did have a gasket, eliminated by 1979 completely and some of the later '78's had no gasket.
 

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So got the crankshaft mic'd today and it's all good (y) the necks measured out 35,98 and 35,975 and they are round.

Have I understood the manual correctly about the bearing sizes? As far as I understood the manual the connecting rods eye's have differing ID'S and they are marked to the connecting rod?

I found some cheap connecting rod bearing 4-piece set that where 36mm but I guess because they are generic they might not fit the rods?

As I have to get a new rod I guess I should wait until I get the rod in my hands and check which number's on the rod and then reference the manual?
 

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Correct. You match the number/letter codes to get the right bearing shells. NOTE: Honda sells the bearing shells by halves so to replace one rod bearing you need 2 bearing shells. At this point I would check the bearing codes for the crank and 1 rod and verify that the actual installed bearing are correct.
 
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