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| lozza59 |
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lozza59
Nova Slayer
Joined: 19 May 2011
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 Posted: 22:44 - 29 Jun 2011  Post subject: cb 125 superdream timing engine up (how??) |
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so i took my engine to bits (top end only) as it was making a loud whirring noise, the cylinder head is worn, but i also learnt the camshaft bearings are worn (thanks teflon mike  )
so i have a decent cylinder head and camshaft to go on however...
once i placed the barrels and head on i have no idea what to do next, i cannot figure out how the cam goes back in with the chain in the way, it seems like it wont go back in, the cams and heads are the same i am sure, dimensions and positions of the cam lobes are the same and im keeping the original cam sprocket too,
i have no idea where any of the timing marks are either
also im pretty sure the tensioner is on its loosest adjustment but the chain still seems to have shrunk!!! this is making it yet more difficult,
any help appreciated thanks |
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| paddlesat16 |
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paddlesat16
Crazy Courier
Joined: 07 May 2008
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| Posted: 22:49 - 29 Jun 2011 Post subject: |
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Teflon Mike and a Haynes Manual are gonna be your best friends 
Regards
____________________
I once saw a bloke shagging a donkey.... in Saudi arabia. Theory Test Passed 26/10/09 Mod 1 Passed 26/4/10, Mod 2 Passed 7/6/10 Current Bikes Suzuki GSX1400 K5, Aprillia Pegaso 650, Suzuki DR350T. |
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| Frost |
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Frost
World Chat Champion
Joined: 26 May 2004
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| Teflon-Mike |
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Teflon-Mike
tl;dr
Joined: 01 Jun 2010
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Posted: 00:37 - 30 Jun 2011  Post subject: |
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| Frost wrote: | In truth it;s piss easy once you;ve done it once. |
Bollox is it! - Its a right ballaching pain in the arse!
First of all make sure that the cam chain tensioner mechanism & blades are in thier slots and lined up in the camchain gallery before you begin. They will NOT go in after you have timed in the cam, becouse you wont be able to get them past the cam-chain sproket.
Tensioner mech on the back, slot the CCT adjustment screw through hole in barel and add lock nut loosely to hold it in place, but DONT try and bolt up the top end through hole in head. Until you have the cam in place, and timed in, caps on and the head torqued down, squashing the head gasket, it will be out of line. Also dont put the CCT blade in the top of the adjuster just yet, or it will 'bow' and put some tension on the chain, and make it hard for you to work round.
OK, so barel on, head on, lets get stuck in.
I have pictures for this on my hard drive somewhere with intension of doing How2: Top-end Rebuild, but none of them are sized, so you will have to use your imaginationand my colourful descriptions.
Engine on the bench infront of you, exhaust ports to your left, inlets to your right, you have the generator rotor ringt infront of you.
TDC is marked on the rotor as TF I recall, but ignore it... through the inspection window in the cover, if fitted, its not accurate enough, and without the cover not even that.
Windscreen washer hose through the plug hole, FIND TDC by feel, and line it up 'on the rock' half way between pipe not coming out of going back in the hole. Leading edge of the induction trigger lugg should be bang on 12 o'clock if the engine's level, and in line with one of the cover screw holes.
Now, the cam, should be inserted. But first remove the cam sproket, and hold it in the Cam Chain galery.
From the back side, slide the camshaft over the head, the cirlcip end YOUR end... looping it inder the cam chain, and into the middle of the Camchain sproket, WHICH you want with the cut out upper most.
Now with the cam chain over the cam, and the cam chain sprocket, on the cam, seat the cam bearings into the bosses in the head.
OK.... NOW the 'fun' Begins!
Rotate the cam in its journals until the slot in the end looking at you is pointing at the inlet ports and is level with the journal boss.
With the Cam in THAT possition and the LH Cylinder at TDC, the cam is timed in.... all you now have to do is get the cam chain sproket on teh cam, and teh chain on the sproket, with teh crank in THAT possition, and the cam STILL in that possition.....
Good Game, good game!
Cam has boos on it with two holes to bolt the cam chain sproket to.
Cam chain sproket has cut out so you can 'drop' it to lift the cam chain onto the teeth... you will do this, then lift the cam chain sproket UP to locate on its flange, and bolt to the boss, to discover that the holes in teh sproket dont line up with the boss on the cam.
You may now, and to yuor hearts content, randomly rotate and lower the sproket to drop the camchain off the crankshaft sproket, rotate it an unknown number of teeth, and try again... its worth a shot, anyway, becouse you will do this unintensionally.....
However... the better way to do it, is to slightly rotate crank to make slack on one side of chain or other, then lift ONE link, and 'roll' the chain round the sproket on tooth, to drop slack off the other end, then lift up, and match up, and repeat until you have the sproket lined up with boss on the camshaft.
When you DO, CHECK the crank possition, AND the cam slot possition.... you will almost certainly have dropped off the crank sproket at some point and fucked it up......
Take NOTE... this is fiffing faffing fidly fuckarsingly annoying.... but its simply patience and try, try again.
And do NOT think, 'Oh, that looks about right' and slap it together....
The cam chain stretches, so the front 'run' gets longer, which puts the crankshaft ahead of the cam, or 'retards' the cam timing, as the cam chain wears, you want to set it as CLOSE to as advanced as you can get it, and the bike will run better, and for longer.
NEXT bit of advice.... if it loops easily as you work the cam chain round, and or the cam sproket slots onto the camshaft flange nice and easily when you mount it..... your fucked.
The cam chain is grossly stretched and probably doesn't have much more than 1000 miles left in it, before it breaks.
You'll be doing this all before the head'c torqued down, remember, so the gaskets wont have squashed. When you DO clamp it down, distance from cam centre to crank centre will shrink a tad....
Hence more reason to be critical making cam as advanced as you can... but also why if the camchain isn't 'tight' on the sproket and the sproket a bit stiff to hook onto its flange, you'll have a LOT of slack n that chain, the tesnioner wont be taking up, when you do hook it up.
ANYWAY, that's the principle, alignments are a TRUE top Dead centre on LH cylinder, which is roiughtly TF mark top of rotor, more accurately leading edge of ignition trigger lug aligned with upper most geny cover hole, but BEST found by feel on the rock with TDC indicator through plug hole.
CAM alignment is slot level with cam-cap boss, pointing inlet wise, (3 o'clock)
Cam chain worked around on the cam, to get it to line up with boss on cam, when on teh flange, and critically set with as MUCH advance as you can get away with.
If needs work the chain round an extra tooth and see what the alignment is.....
ONCE you have it times in, nip the cam chain sproket screws in place, fit rocker assembly / cam caps.. but DO NOT toque them down, do the nuts finger tight...
THEN turn the engine over VERY gently by hand, with a small torch shining through the plug hole, looking at the valves opening.... and make sure that the valves do NOT touch each other or the piston.... and check both pots.
As you rotate the engine, cam will put pressure lifting the rocker assemblies, then relieving it, letting them drop.... so keep rotating the engine slowly and finger tightening all the head nuts holding the rocker caps on, taking up the slack, and getting them to seat nicely, and evenly....
THEN roll motor over again, once the rocker caps are 'home' and MAKE SURE the valves dont touch anything...... THEN return to the cam chain tensioner, and fit that up properly, and attach the tensioner blade, and apply tension.
You will probably have to slacken off the tensioner top nut to let it slide and put tension on the blade, and you'll probably have to waggle the blade to get it to adjust up.
Nip up tensioner adjustor, then do the tappets... then with all 'set' work motor around AGAIN to be sure nothing is gong to touch....
THEN you can torque down the head fully.... AND check valves AGAIN!
It oughtn't be too much of a pain, but it IS, its just niggly!
It is easy to get the cam 180 'about', one of two ways. Either circlip end away from you, or slot at 9'oclock, with LH piston at TDC.
More common is trying to put the cam in 180 about, ie circlip end to the RH side of engine..... do that and it IS possible, cam will be rotating BACKWARDS... not good!
But follow the book, 12 o'clock on the rotor, 3'oclock on the cam, and bobs your uncle!... well, he's my cousin, but I suppose he must be SOMEONE'S Uncle!
Good luck.... patience and beverages, thats what you need!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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| lozza59 |
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lozza59
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| Posted: 23:58 - 01 Jul 2011 Post subject: |
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thankyou again Mike your brilliant!!
took me some time,, a long time and once i was happy i just kept turning it over and checking,
will be placing the motor in the bike again tommorow to see how she runs so im quite excited about that!
also the bolt that goes into the centre of the generator wheel has a threaded hole and nothing to go in it?? is it missing something?
i also bought some carbs from the earlier 't' model cb the choke linkage between carbs is longer, and choke lever is mounted onto the carb , mainly bought them for the inlet rubbers, got quite lucky as they are the same but with no splits! so for 35 quid felt worth it, also being the scrooge i am i found some other inlet rubbers on ebay that look similair,
https://www.ebay.co.uk/itm/Carburetor-Rubber-Flange-24mm-Keihin-PE24-Koso-PWK24-/220519431241?pt=UK_Motorcycle_Parts&hash=item3357fb7c49 |
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| Teflon-Mike |
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Teflon-Mike
tl;dr
Joined: 01 Jun 2010
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| Posted: 10:51 - 02 Jul 2011 Post subject: |
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| lozza59 wrote: | https://www.ebay.co.uk/itm/Carburetor-Rubber-Flange-24mm-Keihin-PE24-Koso-PWK24-/220519431241?pt=UK_Motorcycle_Parts&hash=item3357fb7c49 |
Hmmm will investigate!
Yes, the generator rotor ought to have a bolt down the middle!
Theres a thread in the rotor (M16) to screw in a pullor to remove from crank, then I think its an M10 fine thread in the crank to hold rotor on the taper....
Just taken two engines round my favourite, helpful local M/C shop to get them to put thier fancy hydraulic puller on them....
Haynes Book of Lies says that screwing an M16 bolt in the middle does the job.... £6.80 lighter from Screwfix for a pack of five short M16's...... No it Fucking DOESN'T, Mr Haynes!
Chap that actually 'did' them, reckoned that they came off like a cross bow bolt, chucking the rollers for the starter sprocket every where!
As he put it, "Well, they might have pressed off with a bolt, like the Haynes said, twenty years ago..... but themz wuz BI-IT tought, on t'tepurr"
However.... I have this 'sneaky' little feeling that spinning the crank to 14K a few times, with the vibration of them little pistons on it, and no crank bolt, is possibly likely to shake the thing off, rather well.... when you dont WANT it to, by the principle of Sod.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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| lozza59 |
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lozza59
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Old Thread Alert!
The last post was made 14 years, 287 days ago. Instead of replying here, would creating a new thread be more useful? |
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