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So, I'm just thinking out loud here...

I looked back through the videos I've taken during the process of fixing up this bike. I have video of it right when I got it, which is ugly because the carbs were dirty.
I cleaned the carbs and took this video
and I feel like I can hear the same ugly slapping, pinging noise that it is making still. Somehow (probably because I'm a novice) I missed it throughout this whole process. I think later I ascribed it to the balancer chain being loose but that didn't play out.

You're probably right, taking the engine out makes the most sense. I could buy a donor engine, but who knows what issues a motor in a box might be hiding. I already know the top end of this one is sound. I would have to take it out to stick a new one in it anyways.

Main problem now is that I don't have a shop. The bomb shelter situation shifted after the bike came out. Guess the neighbors upstairs don't like the smell of burnt fuel.... :confused: Looks like it's the living room for this next chapter.
There it doesn’t sound as loud. Trying to diagnose noises via video is almost pointless in most cases. Nothing wrong with the living room. Just drain as much oil out as you can and leave the tank and carbs somewhere else, so you don’t stink the place out. I would just take the engine up there.... if the neighbors see you dragging in a whole bike, then there will likely be some drama.
 

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Discussion Starter #202
Well, took out the plugs and tried the quick test. Both Pistons are solid. So for now that one doesn't help. It could still be a connecting rod bearing but I won't know until I take the bottom case half off.

In doing some more reading, it looks like the two balancers could also be to blame. They both run on a bearing and also use cush drives, which if spent would contribute to the symphony the crank case is making right now.

I guess I'll pull the bike into the living room then. BRB
 

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Well, took out the plugs and tried the quick test. Both Pistons are solid....
You can't really tell squat about the pistons unless you take them right out, it is the ring groves, wrist pin, piston skirts and barrel that will reveal issues with the fit of the pistons into the cylinder. Stuck rings for instance will induce all kinds of nasty mechanical noises on an air cooled engine.

Anti-vibration counter-balancer issues? <- don't buy motorcycles that have chain driven counter-balancers, they suck when they are new and don't improve with age.
 

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Discussion Starter #204
So I pulled the top end off of the bike. Good thing. The valve train is.....showing signs of wear.... I missed this the first time I had it apart somehow.
The camshaft gear was perfectly aligned with the head deck, at TDC for cylinder 1. The valve cleareance was .004 for both intake on both sides, and .006 on exhaust, which is to spec.

camgear.jpg

Camshaft is showing max lobe diameter of 34.44 - 34.48. Spec is 36.99. Is it possible that the cams have lost over a mm in diameter? The rocker arms are showing the abuse from being smacked every time they hit the camshaft. It's possible this was the noise I was hearing all along. The wear on the cams for the left cylinder is much worse. The left side was the more noisy of the two as well. Now I am pretty convinced that I need a replacement camshaft as well as replacement rocker arms, accross the board. I haven't opened the bottom case yet, but I am now not looking forward to what is hiding in there. Starting to feel expensive.
lifter1.jpg lifter2.jpg lifter3.jpg lifter4.jpg
 

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So I pulled the top end off of the bike. Good thing. The valve train is.....showing signs of wear.... I missed this the first time I had it apart somehow.
The camshaft gear was perfectly aligned with the head deck, at TDC for cylinder 1. The valve cleareance was .004 for both intake on both sides, and .006 on exhaust, which is to spec.

Camshaft is showing max lobe diameter of 34.44 - 34.48. Spec is 36.99. Is it possible that the cams have lost over a mm in diameter? The rocker arms are showing the abuse from being smacked every time they hit the camshaft. It's possible this was the noise I was hearing all along. The wear on the cams for the left cylinder is much worse. The left side was the more noisy of the two as well. Now I am pretty convinced that I need a replacement camshaft as well as replacement rocker arms, accross the board. I haven't opened the bottom case yet, but I am now not looking forward to what is hiding in there. Starting to feel expensive.

Cross out “showing signs of wear” and insert “completely fucking knackered”..... and yes that would make quite a racket.
 

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Discussion Starter #210
I actually looked it up and they don't make them. It would have to be a custom cam and roller setup. Possible business opportunity for somebody with a lathe....?
 

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It looks like it was ridden the 50,000 miles with no maintenance done. With the top end so worn you should check the bottom end.

I don't know how expensive used engines are in Germany but I'd do some checking. I have an excellent, 25,000km 450 that, if you were nearby, I'd sell for a couple hundred dollars. You'll spend that much pretty quickly rebuilding.
 

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I actually looked it up and they don't make them. It would have to be a custom cam and roller setup. Possible business opportunity for somebody with a lathe....?
Even a Suzuki 250GSXR motor has rollers now.
... no, you wouldn't use a lathe for that, you would need to get all Bert Monro on it.

Way easier to just find a working engine that you can shoehorn into that rolling chassis, they built millions of them that should pretty much be a direct fit. Make it so before the snow falls ;)
 

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Discussion Starter #213
I've looked at buying a used motor, there are some for sale that are cheap, cheap (like 50 bucks) and some which are cheap like 200ish. I almost pulled the trigger on a 100 euro one in Hamburg, but the guy sold it before I could drive out there. That's the way she goes.

I found some valves used on ebay which look very good for 30 bucks. There is a cam for sale on Ebay which the seller has mic'd and is within tolerance, about 80 bucks. So at this point, if the crank and its various journals are still serviceable, I might get out of this one with only the valve train and some bearings. Probably some balancer weight rubbers.

Might be worth putting new chains in it too, while im at it. Depending how much those cost. Or not.
 

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.... There is a cam for sale on Ebay which the seller has mic'd and is within tolerance....
:eek: you found a seller on eBay that knows how to measure wear on a camshaft with a micrometer ! That would be a rare find.
Send him your old cam and if there isn't obvious physical damage apparent on the surface I bet that passes too.

... every once in a while you should remind yourself what these bikes originally sold for :| they haven't got better with age.
https://honda400four.wordpress.com/2013/07/26/cycle-test-1977-cb400t-the-new-honda-400-hawks/
 

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Discussion Starter #215
:eek: you found a seller on eBay that knows how to measure wear on a camshaft with a micrometer ! That would be a rare find.
Send him your old cam and if there isn't obvious physical damage apparent on the surface I bet that passes too.
Loool... message received
 

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... consider for a moment the friction surface area of the cam, relative to the friction surface area on that rocker arm,
both are protected by only a thin layer of hardened steel. and the cam is rolling on aluminum if it's not riding on oil.
Which one is going to win.
 

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It sounds disgusting.... always hard to diagnose via recording. If you are going to crank the engine over (with starter) with a plug removed, or run it on one cylinder to see if its one cylinder or the other making the noise... don't just let the unused plug lead hang there. Probably best to short it out to ground. If you are just turning it back and forth with a wrench, it doesn't matter. Doesn't sound like piston slap and that would be relatively rare in one of those engines. If something is going to go south due to lack of oil, the cam bearing surfaces in the head are first to go, so "usually" you'll get the death rattle in the upper end first. As suggested, set up the carbs, but before you do..... Adjust the valve clearances, cam chain, and don't forget to adjust the balancer chain. If the balancer chain adjustment has been ignored for a while. that could be a source of at least part of that expensive sounding racket. I would sort that out before you spend money on exhaust etc.
At the risk of sounding like an old curmudgeon ...again.... reread the last line in post 27 ^^^ . If you are going to buy a complete running engine, that makes sense. Buying any bits and pieces before you know the condition of the bottom end does not. If you are going to buy an engine, do try and see it before you buy. Simple enough to pop the valve cover off and “properly” check for wear... if you get my drift.
 

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Discussion Starter #218
The lower case half is off, and I've been poking around inside the crankcase. Right out of the gate, there doesn't seem to be any damage to the crankshaft main journals or the connecting rod journals. The bearings show wear but not excessively so. I have attached a couple videos of it. Fair warning, most guys on this forum are experienced wrenchers and I'm not. I had a hard time finding any videos on the teardown and reassembly of this engine so for the sake of other novices like me, I am recording it.

Main Journals - https://youtu.be/j8Km13ElmGs

ConRod Journals - https://youtu.be/rVa8mXnyjDA

I cant really figure out how to pull the sprocket off of my balancers, heres a photo of the part and the manual image. I'll have to figure out if I can still check for the dampener or if it even has them. For now, I haven't seen anything that would cause the knocking sound i heard. Maybe it was just the valve train doing battle with the camshaft
 

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Looks like that balancer might be a newer version assuming there was one. Can’t tell much from the photo, maybe post a better one. I “think” those rubber inserts are listed to fit 81, but you should check an actual Honda parts list to see if there was a superesession mid run. That sort of thing was done a lot. The factory list will tell you at what engine number the change took place if there was one.
Crank “looks” good. Wear on the balancer chain guides is expected, but can’t tell much from what I saw on the video, although didn’t watch the whole thing.
 

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Discussion Starter #220 (Edited)
German Camshafts.... apparently, Honda produced two HP versions of the old Hawk, and in Germany they sold the little guy. Cam lobe diameter was reduced to 34.5mm from the standard 37mm. From what I've read, you can directly swap the larger camshaft in. But that begs concerns about the domed pistons, or other valve train components needing to be changed. I'll keep reading on it. Theres a honda twins thread on it here.

https://www.hondatwins.net/forums/67-miscellaneous-discussion/4987-cb400t-27hp-vs-cb400t-43hp-2.html?amp=1

This makes me feel better and worse. Still haven't found a good explanation for the damn tapping sound I was hearing. Unless it was the rocker arms...
 
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