1969 T100c Running Rich

Discussion in 'Technical Help' started by Shabuti, Dec 27, 2022.

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  1. capt

    capt Elite Member

    May 8, 2016
    3,052
    750
    western Australia
    On a rebuilt motor the compression can be low ! It needs to bed in. Can take quite a few miles before it will read true values..!
    Perversely it can be "Tight" and requires higher idle speed to "Keep it running" at idle ! Once you have the ignition system working (replaced?)
    Take it on several long rides ! Do as many hours/miles as you can ! Bed it all in !!! I know modern motor's with efi and fuel injection run fine from new and because of their electronics they don't stall as much as carburated engine's, even though they are "Tight" heavy fuel consumption for first 800/1500 km is the norm ! And I've never achieved true good fuel economy until I've had close to 4/5000 km on the clock.
     
  2. Shabuti

    Shabuti Well-Known Member

    Dec 27, 2022
    28
    68
    USA
    Ok. I figured as much with new rings needing time to seat properly. Im not sure how many miles I put on it, but I live on an island thats only about 4 sq miles and many days I would take and ride it around for an hour or 2 at a time. But probably didnt put more than 100 miles or so on it, only went through 2 whole tanks of gas in 2 months. And that was running rich.

    My odometer nor trip meter works on the bike fyi haha. Speedo kind of works but is off a bit.
     
  3. Shabuti

    Shabuti Well-Known Member

    Dec 27, 2022
    28
    68
    USA
    #23 Shabuti, Jan 12, 2023
    Last edited: Jan 12, 2023
    So update, heres a list of what was done on this rebuild:

    -all new boyer mkiv ignition system
    -new boyer single 12v coil with new wires/plugs
    -all new jets and needle for amal 626 carb 106 needle jet and 170 main jet needle set at top notch with new clip as well
    -annealed the head gasket for reinstall, compression is reading 105psi on both cylinders which I feel is still low but should be enough for combustion
    -float bowl reset to about 0.080

    All of that and it still runs exactly the same as before, if at all. Rich as hell, smokey, and will foul plugs now in about 30 mins.

    After the rebuild, I checked the plugs and they had a very strong bright spark, far better than the old system I could barely see at all. Ran the bike up to 3500rpm to check timong and it was nearly spot on 38 degrees btdc.

    So Im officially out of ideas. It has fuel, compression, and good spark with good timing and still refuses to run correctly mostly dying a few seconds after starting. Always dying when put in gear.

    So I have come to the conclusion there are supernatural forces at work here and the bike will soon be going up for sale for $5k firm. Thats not far from what Iv put into it and Im not putting another cent into it. It has new piston rings, new headgasket, new rocker cover gaskets, fully rebuild carb, new air filter, the head and pistons were both completely cleaned near polish on first rebuild, new battery and fairly new chain and sprockets, new throttle and clutch cables, new headlight assembly, gas tank has been cleaned and outside re clearcoated, new front fork boots drained and put in new oil, changed engine and gearbox oils.

    On the up side I have taken this engine apart so many times I can fully tear it down and rebuild in about an hour now. Iv worked on many cars, rebuild many engines, never in my life have I encountered something so persistant on not running. I bought this bike to enjoy rebuilding it, but for all my money and efforts to be wasted and no accompishments to be gained, Im just over it. Mentally exhausted.
     
  4. speeder

    speeder Noble Member

    Jan 3, 2019
    405
    313
    dorset
    Sorry to hear this, it's never easy to admit defeat.
    l am sure myself and others on this forum would love to have a go at it, but that is life.
    Hope you manage to sell the bike OK.
     
  5. darkman

    darkman Crème de la Crème

    Oct 26, 2015
    7,545
    1,000
    Southcoast of the UK Earth
    Silly thing but are you sure you have the choke cable full pulled back so that the choke is in the lifted position. Slack cable choke on and pull lever back for tight cable for choke off.
     
    • Agree Agree x 2
  6. Shabuti

    Shabuti Well-Known Member

    Dec 27, 2022
    28
    68
    USA
    Well, Im back and forth on it haha. I dont like to admit defeat, especially with so much effort put in. Iv actually never put this much effort into anything Iv done in life as sad as that sounds haha but Iv really put my heart and soul into this thing.

    So, after running it for a bit up until the point where it refused to even fire anymore, I noticed there to be a good amount of oil coming from the head gasket on the left side. So much that it had actually started dripping down onto the primary case. Even so, it was still showing 105psi, which is the highest pressure iv seen from this engine since initial rebuild.

    But that got me to thinking, if oil is coming through the outside of the head, it must also be making its way into the combustion chamber and diluting the fuel mixture. And if thats whats happening, must be alot of oil coming in. But from where? Valves guides appear to be good, no oil on back of valves and I wouldnt think they could possibly leak THAT much oil even if they were.

    So given the new piston rings, Im wondering if my rocker cover gaskets are leaking and letting oil pass through the head bolts and down. Would that be a possibility given that no oil goes through the block on this motor?

    Or should I be looking at the piston rings again? With this recent rebuild, first kick psi is around 90psi maxing out at about 105psi. I havent performed a wet compression test yet, but thats a pretty high initial pressure I think if the rings werent sealing it would be alot lower.

    And yes, choke is operating as it should. In fact, I almost always have to use the choke to start it even if its warm. Which given that I now know its not the ignition system, the fuel must be getting diluted to the point where its not burning.
     
  7. speeder

    speeder Noble Member

    Jan 3, 2019
    405
    313
    dorset
    I would have thought that if it's oil getting into the combustion chamber you would see a lot of blue smoke. Excessive fuel usually produces black smoke,and you said the fuel consumption was exceedingly high.
    If you do manage to crack this fault you will probably find that the evidence was there all along.
     
  8. Shabuti

    Shabuti Well-Known Member

    Dec 27, 2022
    28
    68
    USA
    #28 Shabuti, Jan 12, 2023
    Last edited: Jan 13, 2023
    Black smoke appears when throttle is ripped quickly, otherwise its a bit of blueish white smoke with strong fuel smell. But doesnt always have smoke, but always has had strong fuel smell.

    I chocked the smoke up as fuel and not oil, because the oil level did not appear to change and the plugs were dry. Would have figured if was burning oil, there would be other signs. But, it wasnt smoking until 2 weeks ago before this last rebuild. It had been running rich before then, but things progressively got worse and here we are.

    You dont think the new rings would be bad already with so few miles? They are cast iron rings. Should last longer than that I would think. Where else could the oil be coming from?

    Edit: going through pictures on my phone, came across this which was taken after I honed the cylinders which was the first time I had taken the engine apart. Dont know how I missed it, but it appears as if the block has a rather large crack in it. But how would this allow oil through if oil doesnt go through the block?

    Screenshot_20230112_193627_Gallery.jpg
     
  9. Iron

    Iron Elite Member

    Dec 29, 2021
    2,554
    943
    Bob Ross Studios
    #29 Iron, Jan 13, 2023
    Last edited: Jan 13, 2023
    Comes down the head bolts from the rocker boxes...it's really annoying and hard to stop once you get it. I've used dowty washers, some have tried o rings but new rocker and head gaskets are always required. Anneal new copper ones and that sticky copper spray stuff - I've never had any luck with copper gaskets - lots swear by them.
    Looks like new barrels required which will solve any piston slap or rings sizing issues.
    Is that damage the same side as the damage to the head?
     
  10. Shabuti

    Shabuti Well-Known Member

    Dec 27, 2022
    28
    68
    USA
    #30 Shabuti, Jan 13, 2023
    Last edited: Jan 13, 2023
    Im not sure, that picture was taken with the barrels off no idea what orientation it is but next tear down I will inspect closer and find out.

    Iv never experienced piston slap and the only ring sizing issue was when the previous owner installed standard rings on these +020 pistons.

    When I installed the new +020 rings, each bore measured out to as near as I could measure perfectly round at 2.73 inch. And the new rings each gapped perfectly in spec to each bore, so I dont think the bores are effected by this crack. I dont think this crack would be causing my oil leak issue though, if its causing any issue. Maybe some JB weld would seal it up? Not looking to dump another $700 into this given that it did run decently for a short while with this crack.

    I ordered a new copper head gasket, then got to thinking and ordered a non copper one too. Also bought some fiber gasket material to make new gaskets for the rocker covers. I too have decided that these copper gaskets may be the source of my issues if they arnt sealing properly, which it appears they are not at all. And I have never in my life working on engines seen copper used as gasket material for an engine.

    Will probably make the new gaskets for the rocker covers today and see if that stops oil getting in. Do you think the oil gets in from the bolt hole enlarging over time and creating a wider path for oil to travel down? If so, maybe a custom made gasket can seal around it tighter?
     
  11. Iron

    Iron Elite Member

    Dec 29, 2021
    2,554
    943
    Bob Ross Studios
    Your bore measurements do indicate correct sizing - standard is 69mm. (2.717 inches). Piston to bore should be around 4 to 6 thou if I remember correctly.

    Crack may have been due to overtightening of cylinder head due to gasket continued leak. It's important to maintain spec torques on these machines rather than just to keep tightening up due to an oil leak. Could have also been caused by the same damage seen in the cylinder head.
    Detonation of top of piston? Dropped valve?

    Oil will travel down the bolt's thread if it first gets past the gasket. 650 and 750 vintage Triumphs suffer from heads being comprssed locally around the bolt holes in the cylinder heads. Again caused by overtightening of the headbolts, which then do not seal on the washers and allow oil to drain down the threads. I've had this a couple of times, especially with copper gaskets.
    I've tried dowty washers and o rings but always come back to standard non copper gaskets.
     
  12. Shabuti

    Shabuti Well-Known Member

    Dec 27, 2022
    28
    68
    USA
    Yes, the engine was bored 020 over so 2.71 + 0.020 would be 2.73.

    Yea, not sure what happened to the head either. My guess is that whatever happened to the head and piston, also damaged the cylinder wall (and may have caused that crack) and could have possibly been the reason that the cylinders were bored out.

    I never torqued the head bolts down, I just tightened them snug in the order listed in the workshop manual going across from the inside out. Usual head install. I do have a torque wrench, I guess Ill dig it out for the next and final rebuild Ill be doing.

    Im also going to check the head for warpage again, and Ill check the block. I never checked the barrels for warpage I dont think, so Ill take a look there.

    Installing custom gaskets on the rockers didnt appear to do anything. Dont know if it stopped oil leaking but bike still didnt start. So I ordered new non copper rocker gaskets, and will also check the rockers for any kind of warpage.

    It seems to me, after spending countless hours on this bike that the alloys used are really cheap and easy to damage. I mean, I got my wrench stuck and upon removing it I barely pressed it against the cylinder head and a piece of the cooling fin broke off. Tiny peice. But isnt the head aluminum? Appears to be more like white metal as easy as it chipped off. Im no metal expert, but this thing seems a little too fragile to be reliable long term.

    Also not familiar with old british manufacturing, but is this a typical cast job or has it been modified? Both rocker covers are like this.

    20230113_075948.jpg
     
  13. Iron

    Iron Elite Member

    Dec 29, 2021
    2,554
    943
    Bob Ross Studios
    #33 Iron, Jan 13, 2023
    Last edited: Jan 13, 2023
    Both rocker covers have been welded as the cylinder head bolts have broken the rocker cover bolt holes. Again damage from either the engine problem in the past or severe overtightening to stop pushrod tube and/or headgasket leaks.
    O rings under and on the pushrod tubes need to be correct thickness, if the wrong ones are used then they can cause warping of the cylinder head. When placing the cylinder head before tightening of bolts the gap should be measured. I can't remember the 'squish' gap required but think it's about 30 thou.

    The bike should start, even with the damage that's been seen, so there's additional problems somewhere. One of the previous owners knew a lot more about this engine than was let on. Not an engine to trust....good one to get your teeth into though. I'd have it in a flash.

    I always end up completely rebuilding - even engines that are supposedly ok - I've never found one yet that was ok enough just to use.

    Remember, they are 50 years old and have been owned by ruffians with only a hammer and a pair of pliers to keep them going.
     
    • Like Like x 1
    • Agree Agree x 1
  14. Shabuti

    Shabuti Well-Known Member

    Dec 27, 2022
    28
    68
    USA
    #34 Shabuti, Jan 13, 2023
    Last edited: Jan 13, 2023
    That was my fear...looked like a weld job, but at least a halfway decent one I suppose. Someone really did a number on this thing, and Im starting to lose confidence that I can undo whatever was done to it.

    Im just going off of basic physics at this point, all else aside. Because when I rebuilt the engine the first time, with new piston rings and a clean head it ran. I did not realize the carb was not jetted properly due to the documentation that was provided to me, but even so the bike ran. And for the first month it ran pretty good all things considered, no smoke and at first it didnt have a strong fuel smell.

    Somehow, with use the mixture either got richer, or the engine stopped burning it efficiently. My guess was the ignition system, which did appear to produce a rather weak spark compared to this new one so it probably needed replaced. The next guess is the low compression, must be due to gasket leak that I presume existed the whole time after the first rebuild. Perhaps after running it a while, the head gasket began to leak more dropping the cylinder pressure to the point where between low compression, oil diluting the mixture later, and weak spark it couldnt run anymore. Well, it ran enough to idle but not enough power being produced to handle any kind of load.

    But, now with this last rebuild the cylinder pressure is higher than it was before, so theres certainly enough compression (hopefully a new gasket boosts that up to the 135psi it should be at) and the spark is on time and strong. That only leaves the oil getting into it and diluting the fuel, but in most cases oil will burn with fuel just fine. So that has to be a large amount of oil flooding the cylinders right? I can now see light oil coating ontop of the piston heads. I wouldnt think valve guides could leak that much oil to flood a cylinder, so it has to be the head bolts. But could the head bolts even allow that much oil to flow into the cylinder? Im sure you also noticed from the pictures, when taking the head off theres alot of oil on the gasket itself and the piston heads.

    Iv gone back and forth about putting new rings in....but given how new these are, and the initial pressure produced I cant see them being the issue. Also, I presume there are no oil jets spraying the back of the pistons, so its basically just tossing the oil around with the crank right? So even if the rings were bad, wouldnt think that much oil would be passing through as if they werent even there right? The first time I fired the bike up before taking anything apart, with the rings having about a half inch of gap the engine still started and ran, just smoked out the whole neighborhood with the amount of oil it was burning.

    So you also agree, that even with the damage to the pistons, head, and rocker covers, the crack in the barrel that provided I get this oil under control the bike should run?
     
  15. Iron

    Iron Elite Member

    Dec 29, 2021
    2,554
    943
    Bob Ross Studios
    The bike shouild run even with the oil leaking down the bolts and up passed the pistons and down the valve stems. Even with wet sumping I've never seen an oil leak so bad that it would stop the bike running.
    There'd be lots of smoke and it'd run rough, I suppose given enough to act as a hydraulic brake it'd stop like being siezed but no, it should run.
    So, I think there's something else afoot as well.

    Ignition switch not working, bad connections, battery too low voltage to fire electronic ignition, valve timing could be off, cams could be bolloxed, bushes worn really badly or cracked. I've seen teeth missing off of timing pinions. Air and/or fuel starvation or flooding? Do you have a sump full of oil? Sludge trap completely blocked with PRV letting by. Unfortunately the list goes on.

    It could just be a loose connection which, when fixed, could solve everything.

    I'd be cracking out the spanners and getting into it. There's fuck all on tv anyway - the Raiders were a disgrace this year :)
     
    • Like Like x 1
  16. Shabuti

    Shabuti Well-Known Member

    Dec 27, 2022
    28
    68
    USA
    #36 Shabuti, Jan 13, 2023
    Last edited: Jan 13, 2023
    Hmm...well, ignition short is entirely possible. I rewired the ignition, but did not change out the switch itself and there is a bit of play in it. But I intially ruled it out because every time Iv tested it using a timing light it never showed signs of being an issue. I also feel like with the other symptoms it doesnt really indicate a short but it could be an existing problem that just happens to be existing amung other ones haha.

    Battery is at 12.6v. The oil level was full last I checked, I can check it again. Probably gone down a bit now as Iv been cranking it with the oil tube off so its squirted a good bit of oil out.

    I just did the rocker covers today, and every time I install them I always ensure valve actuation as those pushrods are a pain in the ass to get right...especially with home made gaskets haha. But, the valves are operating normally. Cant see the timing being off, I havent touched the timing cover yet but the valves do appear to open and close at the proper times.

    Can you explain the "sludge trap" and PRV a little bit more? Not familiar with that, the sludge trap I assume being the oil "filter"? Also, when you say sump are you referring to the area under the crank or the tank the oil sits in? The area under the crank isnt "full" of oil, theres a level of oil in it.

    In the meantime, I will go ahead and bypass the ignition switch altogether and see how that goes. Not like anyone can steal it anyway :p
     
  17. Iron

    Iron Elite Member

    Dec 29, 2021
    2,554
    943
    Bob Ross Studios
    There's no oil filter as standard on these (lots of owners have added after market filters). The oil is pumped along the centre of the crankshaft and out through oil holes in the big ends to keep them lubricated. It then just splashes around in the sump keeping everything oiled until it is sucked up by the scavenger pipe back to the return side of the oil pump.

    The spinning of the crankshaft acts as a centrifuge to force the heavier particles in the oil to the outside of a large diameter removable pipe within the crankshaft. This is the sludge trap. If it becomes blocked due to the sludge building up then the big ends do not receive enough oil with obvious results.

    The PRV (pressure relief valve) is a simple piston on a spring that is on the oil delivery side of the crankcase. As the pressure builds up it moves the piston against the spring to allow oil to bypass the crankshaft delivery and drop straight into the sump. It operates every time the oil is cold and thick on start up so as to not blow every o ring and gasket. Once the oil is warmed and the pressure drops slightly then all of the delivery oil is pumped into the crankshaft. If there is an obstruction, (ie sludge trap almost blocked) then the pressure builds, oil leaks get worse and the PRV will allow oil to bypass into the sump.

    I've rebuilt engines that looked pretty bad and found the sludge trap to be really clean as previous owners kept up on maintenence and oil changes. I have just rebuilt an engine that was 'sparkling' - supposedly completely rebuilt by a dealer with a sluidge trap almost full to the brim. I'm doing a rebuild now on an engine with only 14k miles confirmed on it, the sludge trap was 75% full.
     
  18. Iron

    Iron Elite Member

    Dec 29, 2021
    2,554
    943
    Bob Ross Studios
    The sump is the crankcases that contain the crankshaft. It should only have a cup full of oil in there - about 100-150cc.
    The return side of the oil pump has a bigger piston than the delivery side so, in theory, the return will continually empty the sump down to the scavenger/suction pipe. The pipe can be seen when the sump plug is removed from the underside of the engine. The sump plug holds a mesh to ensure no large particles are sucked up the return pipe.
     
    • Like Like x 1
  19. speeder

    speeder Noble Member

    Jan 3, 2019
    405
    313
    dorset
    Iron is correct, I've had quite a few old bikes and cars, and always found that the majority of the work required to get them properly sorted usually involves correcting "bodges" that have been done by previous owners, ans some can be very subtle...it once took me months to find why an MGB would not run properly, like you l went through everything only to find in the end that someone had fitted the wrong camshaft.
     
    • Like Like x 2
  20. Shabuti

    Shabuti Well-Known Member

    Dec 27, 2022
    28
    68
    USA
    Thank you for all the clarification on the oil system on this bike, the workshop manual diagram was kind of confusing it didnt really show how oil got to the crank just how it runs down from the rockers.

    Also, rebuilt the motor again today with the old copper gaskets. Annealed all of them once again, but this time I let them air cool didnt dip them in water like they said to. I also took 220 grit sand paper and lightly evenly sanded the rocker covers, head, and the barrels so everything was smooth and clean to mate.

    Also, that wasnt a crack in the barrel. It was just some gunk, cleaned that out too. So no cracks.

    I also bypassed the ignition system. The result is a one kick start now. No smell of fuel at idle, or riding. Hard revs still show a bit of black smoke though, and its still burning and leaking oil through the head gasket.

    So, took this opportunity to get a video of it actually running, and running pretty good I think. So you all can see it.



    So perhaps the ignition switch was causing issues, Ill replace that. Will also do a full, clean rebuild with new gaskets when they come in.

    Iv figured out that 50 year old screws cant handle being threaded over and over again, Iv been replacing them as I go but today I lost all the threads on 2 of the rocker cover studs so now I have to replace all 4 of those.

    I did also clean out the threads for the headbolts in the barrels, there was definately a puddle of oil inside where the head bolts thread. Made sure every thread was clean and everything screwed in smoothly. Head bolts are in really good shape compared to some of the other bolts Iv replaced.

    So, until the new parts come in she seems to be running good right now. Doesnt smell rich, will check plugs. Took it on a short ride today, did great. Nice and smooth take offs, but if Iet off the throttle at anything below 2k rpms while in gear its a little lurchy and jerky.
     
    • Like Like x 3
Loading...

Share This Page