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Post by comstar on Oct 21, 2021 16:02:13 GMT
I bought this 1980 CM400T on a whim this week. Was on Facebook Marketplace about two hours south so I took a chance and had a courier get it (bought blind). Felt it was worth a chance at 700 USD (approx 500 squid).. Had chance to charge the battery and try and start her yesterday after carrying out some basics (she's sparking like the 5th November so we are all good ignition wise). Who's fairly 'mechanical' SD/CM engine wise and up to have their brains picked then?   |
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Post by buster on Oct 21, 2021 17:43:35 GMT
nice buy nick. you'll have to hang on tight to that one, green ones go like stink  by all means pick away I'll help if I can |
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Post by McLellan on Oct 21, 2021 17:53:29 GMT
Ooh that a nice looker liking the green.
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Post by The Great High Lord Beer on Oct 21, 2021 18:10:22 GMT
Good looking machine, hopefully a thorough service and a carb clean will see it right 👍
Of course I always worry when I see mismatched tyres, previous owner on a budget, or limited competence 🤔
But, I'll put a fiver down that after not much work it will be just fine, I would have bought it at that price, well done Prince Comstar 🍺
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Post by comstar on Oct 21, 2021 19:02:16 GMT
Thanks chaps......I know the right level of mechanical knowledge is here from you 'engineering types'  so I will run by you all I know so far. Firstly, a bit of a back story. I agreed to buy this CM400T last weekend on the strength of being able to obtain a second bike for spares that I had already seen some weeks back, although the auto version, a CM400A. This CM400A has only done 11k from new. But it does not have a title (log book) and the seller thinks the engine is 'stuck'. I viewed this CM400A on Sunday night, it was not too far away. Indeed engine seems stuck - kick start shaft seems to be stripped? It was up at 400 dollars or best offer. Seller could not find the key so I offered 275 and he kind of agreed. I said 'if you can find the key I'll give you more' to which he said, no problem, I will look around and come back to you. To cut to the chase, we have got to Wednesday and he hasn't contacted me back......so I call him and he says 'Oh I forgot to mention, someone did leave a deposit on the bike about a month ago and I want to give the guy the chance to get it. If he does not come back to me this week it's yours'......suffice to say, he is now dicking me around it would seem....a lot of this goes on here. I really would like that CM400A as it has so much good stuff on it......stuff (with shipping) that would cost me at least twice as much if sourced via ebay etc. The green CM400T is nice, but parts from this CM400A would put it into a different league cosmetically for sure. Here it is :    |
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Post by comstar on Oct 21, 2021 19:04:48 GMT
Good looking machine, hopefully a thorough service and a carb clean will see it right 👍 Of course I always worry when I see mismatched tyres, previous owner on a budget, or limited competence 🤔 But, I'll put a fiver down that after not much work it will be just fine, I would have bought it at that price, well done Prince Comstar 🍺 You'd hope so but I think we have more of a sinister issue going on (will divulge). The young kid (courier said he was a kid) clearly didn't have a clue about the correct amount of oil for example. Yesterday I extracted very clean looking excess oil from the crankcase- more than 2 litres of excess, it was halfway up the dipstick !!!! So I am in no way surprised the tyres don't match my lord. |
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Post by comstar on Oct 21, 2021 19:13:21 GMT
So back to the bike I have bought.....
Battery on.....starter pressed. Starter is trying but not turning the engine. So I think for a minute......then put bike in top gear and rock it back whilst easing the clutch in and out.
Try starter again with clutch in and engine starts to spin.....but it did not sound right.....that sound as if the spark plugs are removed on an SD and it seems to be spinning without the 'chug'....
As I said, plugs are sparking and plugs even look a lovely colour from when it was last run. Then we get to a point and the starter stops again.....but is still trying. So I do the same and rock the bike back - same again, starter turns but does not sound like it is properly under load - almost spinning faster like. There's more, bear with, just got to pull my toast out the toaster.
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Post by buster on Oct 21, 2021 19:27:29 GMT
yep grab your toast before it goes cold. I'd whip the rocker cover off and the stator cover, then you can slowly crank it by hand and observe what the valve gears doing
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Post by duffer on Oct 21, 2021 19:34:56 GMT
One of the "It ran when I put it in the shed 15 years ago " bikes I picked up, had a similar problem. Spun over easily plenty of sparks...
..no pistons....
Ran when I put it in the shed....my arse.
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Post by The Great High Lord Beer on Oct 21, 2021 19:42:09 GMT
Hit it with a hammer, what could go wrong 😁🍺
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Post by buster on Oct 21, 2021 20:00:12 GMT
the automatic is interesting too, bit of a bugger if its seized and the kickstart shaft is stripped (its not as if you can put it in gear and rock the engine over) the up side is that with a 250 spec cylinder head and roughly 250 spec carbs they physically cant over rev, I was amazed at the good condition of the barrels on mine, also the cush rubbers in the balance weights were in really good condition too.
one of the areas I would be cautious of is the electrical system, have a gander under the left hand side panel, below the panel with the rectifier on it there should be a couple of relays that are linked to the gear change (what would be neutral on a 'normal' SD) and operate the gear indicator lights. any bodging of those wires is a bad sign, the switch and relays control not only the lights in the 'tacho' but are something to do with halving the ignition advance to 7.5 degrees to allow 1st gear to engage smoothly.
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Post by comstar on Oct 21, 2021 20:01:34 GMT
Thanks chaps....all fed and watered now and ready to continue the story......that's for those who are still awake.  Duffer, yep this is the risk with buying blind. Seller sells it with description 'stopped working, I don't know what is wrong with it, I am not mechanical'. I may be stealing that very line for an advert very soon. My desires of an easy repair have now vanished, was hoping it was a spark issue - I even polished my left over from Hawk spare CDI in anticipation before the bike arrived, but not meant to be. Paul, yes this is my next plan of action I think.....will get the rocker cover off and genny cover...... Anyway...so with each plug out (in turn) I press the starter with my finger over each plug hole. Right seems normal and is really pushing out some pressure. When done of the left side, not much pressure being heaved out on my finger. Also interestingly, left plug is getting wet......right one is staying as dry as a bone. I wonder if there are any clues so far before I remove the covers? I think the carbs are okay as I reckon this bike has been ridden certainly within the past few months, the tags (basically tax) still has five months left on it, it has not been sitting long. Oh also, when the starter is pressed, the oil pressure light goes straight out as per normal....I also shone a torch in through the dipstick hole and all looks really nice and as it should be in there on the clutch side. I also noticed that someone has been in this engine before - there were remnants of non factory sealer around the base gasket. Everyone's an engine builder and engineer.....right?? |
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Post by The Great High Lord Beer on Oct 21, 2021 20:14:09 GMT
Start with the basics, assume carbs are full of shite and go from there, my SD is about as good as it gets but after leaving it for a couple of months it's a pig to start, used a couple of times a week it's fine. Time to get dirty I think, a compression gauge may be a good idea as well, after that eeeek 😬
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Post by comstar on Oct 21, 2021 20:26:59 GMT
Start with the basics, assume carbs are full of shite and go from there, my SD is about as good as it gets but after leaving it for a couple of months it's a pig to start, used a couple of times a week it's fine. Time to get dirty I think, a compression gauge may be a good idea as well, after that eeeek 😬 Of course....but I honestly think the carbs will be a secondary issue for now....the engine is not making the right sounds to me, carbs aside. I have three possible avenues now. For now the bike is under a tarpaulin in the the back garden whilst I crack on with the Bonnie. 1) Simply sell the bike on with unknown fault and aim to recoup as much of my money as I can...do I need this hassle right now? Maybe I do. 2) Grab this unknown condition 200 dollar engine which is about an hour north (see pics). Probably not realistic, as although seller claims this engine he thinks is good, I have no proof. And look at the state of that flywheel due to someone nicking the genny cover....maybe the rest of the motor is like that inside who knows? 3) There was a third but I can't remember what it was. Basically I am not giving up on the original motor yet, these are just back up options if the motor is found to be not viable to repair. As you say, now maybe the time to get mucky and learn about the internals of these motors....I have been lucky up until now. By sharing this on the forum, at least some good will come out whatever the outcome in the shape of knowledge for all. If I decide to persevere with this bike I will of course put it in the resto section of the forum, but right now I'm not sure. There is not an option here to use a repair shop on this project (and value of bike) as the labour rates are just too high......basically I am on my own (physically).   |
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Post by buster on Oct 21, 2021 20:31:05 GMT
ouch!
I hate to say this (sorry before I even begin) but please dont turn that engine over again before you get the rocker cover off. gasket goo on the base gasket for me is a walk away scenario (again sorry for bad news) theres just no way you can be sure that the critical oilways are not blocked/restricted, if they are blocked the oil light will probably still function as it should (pressure switch just below that oilway). if the valve gear is functioning as expected (though from what you've said I'd suspect maybe a bent inlet or two?) then check that oil is coming up at the outer cam journals, paying very careful attention to the one on the stator side, if its not flowing well its a top end off job
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so I will run by you all I know so far.
