1969 T100c Running Rich

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.

 

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.

 

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.

 

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?

 

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?

 

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.

 

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?

 

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

 

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.