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zombie_dave
Borekit Bruiser
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| P.addy |
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P.addy
Red Rocket
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 Posted: 10:35 - 02 Nov 2011  Post subject: |
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In theory its that old its probably lost about 3hp  so you should be ok.
Unsure if you can do that, would assume the valves/timing/cams would be slightly different. Teflon-Mike will be in here in a minute, CB125TDC sense is tingling |
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zombie_dave
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| Teflon-Mike |
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Teflon-Mike
tl;dr
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Posted: 12:56 - 02 Nov 2011  Post subject: |
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The head wont make any difference at all.
Identical castings; valves are the same part number.
Only difference is its painted gun-metal not black.
If you have the cam, though, even if its eaten its bearings, I have a 'use' for one, if its going begging
If you are running the PD26's, on UK spec TD-C motor, you are likely to find that the motor will 'bog' quite badly on pick-up. The TD-C motor was 'tuned' to run on PD24's.
If you fancy a trundle over here, can have a play, and I have quite a lot of 'bits'.
What did you do with 'old' siezed engine? And did you swap cases to fit kicks-start or how did you manage to get the e-starter in under the down tube? PLEASE dont tell me you just bent it out a bit!
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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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zombie_dave
Borekit Bruiser
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| Teflon-Mike |
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Teflon-Mike
tl;dr
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| Posted: 14:22 - 02 Nov 2011 Post subject: |
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| zombie_dave wrote: | hi mike,
i have the whole head - including the cam (should have stated that)
the engine casings are original to the tdc engine......... im not going to lie i didnt do the electrics....... i gave it to a friend of mine to sort- all i had to buy was a relay and the right hand switch gear of a later bike.
i had the frame modded properly. so the tube was cut then welded back into position and a little gueest plate added to ensure it was strong enough.
so am i better off just changing the cams? - will that effect the cdi's though? - e.g timingh will be wrong?
the old engine i gave to my mate who is a mobile bike mechanic, i dont hink he has done anything with them though if u want them? - il see if he hasnt slung them out!
where abouts are you based as id be more than happy to have a little ride over to you and the end of the month- ish so you can have a look. |
OK, well, if you have the cam.... bring it over. (I'm in Nuneaton) First thing to do is check it against a TD-C cam and make sure it is a genuine 'T' spec camshaft. If not, absolutely no point fitting it.
The CB125 is notoriouse for camshaft siezures; just becouse it lived in a T-motor, doesn't mean that its the original cam.
Commonly replaced with TDC cams when they 'went', or robbed out to go in to super-dreams (depending on age, though, didn't always fit)
Dropping that cam in Super-Dream motor.....
First up; I have been trying to get hold of genuine T-cam for over a year; they are not common, and even rarer in serviceable condition. (as said, prone to cam siezure, wrecking support bearings, but quite a 'radical' profile, they suffer 'peak' wear quite badly.
If nothing more, I would like to 'clock' one up, and get the timing and lift data off it, to be able to get a TD-C cam reconditioned to T-Spec if all else fails.
If you brought it over, could do that checking its not a TD-C profile.
After that....
Well, ignition is not a problem. TDC came in two guises, UK 'Reduced Effect' and rare 'full-power', which was as TDC, 12v DCi ignition, and used same igniter boxes.
But rest of the engine could be.
Super-Dream lumps, are rather flakey; they can loose a lot of performance very easily, and the small loss of compression not from 'bad' bore wear, just worn rings that have lost sharp edge can seriousely dent the performance of 12bhp Reduced Effect engine, effect on 17bhp full power version would be even more dramatic.
The valve seats, loosing thier corners is another cause of lost performance, and they are a pain to re-grind, and double angle the valves, becouse they are so small.
The 'sloppy' cam-chain is next big power robber, prone to stretch, it retards the cam badly.
Old addage of racing, before looking for more than standard, make sure you have what you should AS standard.
Slapping T-Spec cam into head on TDC motor.... yes it will give more power; but probably not as much as it should, and pottential is there, that extra power will simply burn out what 'life' old engine may have faster, if not cause major maledy.
The more radical cam profile, will be a double edges sword, slamming valves open faster, possibly further, it will load both the cam bearings and cam chain a lot harder, leading to accelerated camchain stretch.
Retarding cam-timing, pottential is, especially as the valves open across each other, for valves to tangle to contact piston....
I have had an engine do this with milder TDC cam, and results are NOT nice!
So, to get the 'full' benefit, and avoid it merely making up hole in lost performance, and to avoid premature failure, I would be disinclined to fit T-Spec cam in 'old' TDC motor...
I would do it as part of considered engine 'build' (which is plan, that I have been scoruing for T-Spec Cam for the last year and a bit for!)
Complete tear down; crank pressed apart, and reconditioned, with all new main & big end bearings.... that's would be the (expensive!) start. Building back up, I would not use the cheap generic replacement barel & piston kits I have (quite successfuly) on RedEf spec TD-C's, becouse of the lost 'edge' ring problem. I would have barel rebored with close tolerence finish, and fitted with Japanese pistions and high grade rings. Bottom end assembled with new DID Japan, (again, not DID Tiwan Chines market grade!) Cam Chain, new CCT Slippers, and then the head properly reconditioned, new valve guides, seats properly ground, NOT just lapped, and either new valves or properly (expensive) double angle ground originals.
Rocker gear would them come in for attension, no point having high lift cam if its being robbed by rockers slopping on worn bushes....
THEN I would fit and critically time in the cam, probably slotting the cam sproket to be able to 'vernier' time it.
Cost me over £200 to rebuild last Super-Dream engine, no where NEAR that standard.......
So I would think carefully about it.
Idea is sound, and great to have that bit more 'go', but if as you say, its not a forever bike (one I am trying to build IS), and its just a get-about until you take tests, and step up to bigger bike, then old addage of a bike in hand, is worth tow in the shed, and if it ent broke, dont fix it, springs to mind.
I very much doubt you want to spend the sort of money; £70 for cylinder bore, £80 for pistons, £40 for cam chain, £30 for camchain tensioner slippers, pottentially £150 for crank reconditioning & balencing... how much we up to? Probably about £500 or so to make it 'good' enough to run reliably with that cam...
And popping it in on old bottom end, could be quick route to hassle for small real gain.
But, want to pop over, can have a look at cam, poke prod and generally talk little twins! You can have an oggle at Snowie's 'Pup' that would ultimately get the 'super' engine suggested, and the half dozen other 125 twins I have knocking about....
Old bottom end? well, and CB125 bits will find a home in my back garden that is rapidly becoming a 'Super-Dream Sactury'! I have another siezed T motor appear a few weeks ago, possibly in a similar state; removing rocker cover revealed that original cam had eaten the head in top end siezure; and been removed and never replaced. Or that would have been a candidate for the Pup's build! But have numerouse other's knocking about, and where cases are chewed or heads eaten, bits is bits and if I can put anything to use to make one decent engine ot of them and save yetr another old Honda!
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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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zombie_dave
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| Posted: 14:37 - 02 Nov 2011 Post subject: |
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cheers mike!
sound advise mate, il see what bits nick (my mate) still has of the old engine and when i pop over at some point towards the end of the month il bring them with me.
i think il probably leave the cams alone for the time being until i decide whether il sell the bike on after test etc or run it as a commuter.
thanks for the advise mate! - also il pm you a bit nearer the time for your address! 
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Teflon-Mike
tl;dr
Joined: 01 Jun 2010
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| Posted: 16:08 - 02 Nov 2011 Post subject: |
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| zombie_dave wrote: | cheers mike!
sound advise mate, il see what bits nick (my mate) still has of the old engine and when i pop over at some point towards the end of the month il bring them with me.
i think il probably leave the cams alone for the time being until i decide whether il sell the bike on after test etc or run it as a commuter.
thanks for the advise mate! - also il pm you a bit nearer the time for your address! |
All good.
Just thinking in the car as I was waiting for Snowie; other 'quirk' of the Benley engines is that the cam 'caps' are the rocker bosses, and they are all located on the barel studs.
Swapping a cam isn't a simple case of lifting off the rocker cover, wipping of the cam caps, swapping cam, timing in and re-bolting.
Losing off rocker boss nuts. takes the tension off the barel studs. Head gasket still claped partially by the head bolts, BUT with major sealing pressure on the barel studs, disturbing them, often leads to base gasket oil leak, head gasket compression loss and premature HGF.
REALLY, its a full top end re-build, and you need to lift barels to renew base gasket, and build back up.
Doing that; usually prudent to inspect bore & rings, and knowing piston ring issue, at least a ring replacemnt if not rebore or even as the Chinky barel kits are as cheap as rebore & over size pistons, new barel kit..... you then get into chasing hpeth's of tar... as if the cam times in easily, means the Cam-Chain's fucked! And to change that, you have to pull the crank to loop new one over, and while you have that out...... and so it goes in incrementally!
Hence the if it ent broke advice!
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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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zombie_dave
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| Posted: 10:45 - 03 Nov 2011 Post subject: |
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thanks mike,
i think il definatly not bother.
i think im better off concentrating on doing tests
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zombie_dave
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Teflon-Mike
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Jura55ic
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P.addy
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Teflon-Mike
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Old Thread Alert!
The last post was made 14 years, 347 days ago. Instead of replying here, would creating a new thread be more useful? |
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