Britbike forum Forums Projects started by Britbike forum members Members bike projects 1966 Triumph T100SR Project

Here is an update: I put the bike back in the shop and because I can't leave anything alone I pulled the tank and drained the contents. I discovered a tiny weep around one of the rear mounting bolt holes. I am sure a little sealer will fix this issue. then because of the backfire issue I swapped the points leads on the coils. (But how to test?) I shot a little carb cleaner down the throat of the Monobloc, flipped on the ignition and kicked it a couple of times. I was rewarded with a sweet sounding rapid fire staccato. It's very quite and reserved and not at all like my Norton.I am stoked. I am sure I can get these carb issues ironed out with a little work.


Picture take with the bike out of the shop.

I have been thinking about getting one of those. They are still available but kind of pricey plus you have to add some to the price for the longer screws. I am trying a little red Permitex gasket sealer. It's the same stuff I used on the crankcase.

I got the Monobloc bowl cover sealed. I lapped the carb surfaces, cleaned up the cover surface with wet dry 400 grit and coated both sides of the gasket with red Locktite sealer. This is the stuff I used for the crankcase that never hardens. The bike runs and it returns oil to the tank. That's the good part.

It only runs when I tickle the heck out of the carb. That's as far as I got before the rains rolled in.

Edit: I did check the timing and I had it several degrees too far advanced. I do not know if that would keep it from running but I have to turn over every stone. I also pulled all my carb jets and they are to spec for this year model and they are all open and clear.. The carb is full of fuel too. When I have a bit more time, this evening, I am going to check the manifold gasket.

After this mornings timing reset I pulled the bike out of the shop for another try. It started better, ran just a little longer but only on the tickler. It acts like the Monobloc is not picking up gas. I do not have much gas in the tank, maybe 4 or five pints but it should be enough to start it. Maybe I should get more gas?

Maybe check that the float isn't catching on anything.

I was thinking about this but if the float was sticking the tickle button wouldn't work. Either it would burble gas out or it would not burp a little gas out when depressed (which it does.) Also, when I have pulled the bowl cover you can see the line left by the gas half way across the float. The carb is full of gas because I drain it, at the lowest point, before I put it away. I am going to go back through the carb with a fine tooth comb. I thought I did before but maybe I missed something.

I also made a degree wheel for the points cam and I am going to make damn sure the timing is spot on. Then I am going to get some NGK B7ES plugs. It has new Champion N3C plugs and I was never a Champion plug fan.

You may want to check the petcocks. I have had old ones lose capacity due to the seals failing. I ran a drill through, but had better luck replacing them.

It does help and I appreciate it. I have been thinking along those same lines especially adding more and pulling the bowl cover to actually see the fuel flow. I did pull and inspect the jet holder and all is clean and the jets snug. I did get another gallon of non-ethanol fuel.

I never used the tickle button to keep the bike going. It only started and ran a few revolutions before quitting. It was only with the tickler was I ever able to get it started. (both pipes were hot by the way.)

I was thinking it might be one of several issues that come to mind:

1) The spark plugs are new Champions but I have seen bad Champion plugs out of the box. I am an NGK guy

2) Need more gas as we discussed. Personally I am leaning toward this as the cause. There is just not enough pressure to make the float needle work properly.

3) Manifold air leak but I doubt it since I know how they were assembled.

4) A timing issue and I rechecked that this morning.

5) I am using the 6v coils on a converted 12v system. I may have a weak spark. It seems to me that a weak spark would not fire under the rich condition created by the tickle button.

James,

Risking telling you something that you, as a long-term Triumph mechanic probably already know, I wonder if the slide in your Monobloc moves freely through its full travel? With the engine off, if you twist the throttle grip wide open and then release it, can you hear the slide hit bottom again? The reason I ask is because of the leak you mentioned on the cover for the float chamber. That is often a sign of the carburetor body having been distorted by someone overtightening the mounting flange nuts. If the body is distorted enough to leak at the float cover, it may be distorted enough to have the slide stick WFO! That would be exciting with no kill switch, but I see you have wisely installed one of those.

Ray

Yep, having had first hand experience with stuck carbs and wild rides (mostly Mikunies on Nortons) I did check the slide operation as one of the first checks when I got the carb back together.

By the way, there is no risk in pointing out anything to me. It is shocking how much I have forgotten.

I followed your directions but I used the plastic cap from a spray paint can in place of the cheap Chinese take way dish. It didn't melt. What I found did not surprise me. The gas flowed well when the gas was turned on. The needle stopped the flow when the float was raised but when the float was lowered nada, zip, zero. The needle stayed in place. This may be a product of too little fuel in the tank or it just may be a sticking needle. It also could very well keep the bike from running past the initial tickle.

I replaced the needle with a spare I had left from a bag of Monoblock parts I had on the shelf. This needle didn't seem to suffer from this malady. I also buffed up the brass platform on the float that the needle rides on and I cleaned up the hinges with a bit of fine wet/dry sand paper. I wanted to make sure nothing was binding and in that regard I took a file to the spacer and cut just a bit off each side.

It's raining now so the true test will have to wait. I do not try and start the bike in my work shop. It spills too much gas for me to be comfortable running it in a confined space over wood floors..

After all that, no joy. I got home from work, added a gallon. and I got the same result. It will start on the tickler but not run. It's time to pull the carb back off.

With the carb on the bench I started to focus on the pilot circuit. I thought I did a good job with the initial cleaning and building but I was wrong. The pilot jet was stopped up at the small tapered end. The circuit was stopped up behind the mixture screw and I used a piece of fine wire ti make sure the small orifice in the venture was open. I shot carb cleaner through to make sure. I will do this again before I put it back together. I have no hope that this is the running issue but it couldn't hurt.

Well Big Jim I've read through this thread and had a good chuckle because I went through most of this on my 72T100R that I bought in disassembled pieces.
Good heavens the wiring on that thing had been cobbled by every Tom Dick and Harry who touched it but I found a repro cloth harness for reasonable from England
You're plugging along just fine and that is a fine-looking old beast
I like the Monoblocs - I had a lot to learn with my twin Concentrics and I am still sorting them out.
Maybe back to the bench with mine is the best bet

Oh the wiring?? That ancient cloth covered throw back to brittle insulation and previous owner installed crimped connectors? Once I get the bike running and sorted I'll have to strip it down for cosmetics and rewiring.

These things take time and an attention to detail. I think I got in a hurry on the carb. It is a mistake I intend to rectify.

Success! (Sort of) I cleaned the idle circuit last night. I cleaned it again this morning. I slapped the carb back on, added a gallon of gas and hooked up the positive battery cable. A tickle and a kick and she was running, and I mean really running. A total vroom vroom.. I checked the oil return and it was. I checked the battery voltage and it showed over 13,56V at what was probably 3K.

Then it quit. It's back to the same old same old. Tickle it and it will start. Now I am pretty sure it has trash in the circuit so it is back off with the carb but with a lighter heart.

I think both you and I may be cleaning out our fuel system one idle circuit at a time
Shot some carb cleaner and compressed air through mine while mounted and there seemed to be some improvement
Got some adjustable floats coming and I'm making up a mount for an O2 sensor to band onto the tailpipes to compare halves

I checked the plugs just now and they are dry but sooty. I need to check my needle height. I pulled the carb back off and apart (again) and nothing obvious jumps out. I traced the circuts, shot carb cleaner through and the opening seem clear. I think these Monoblocs are robust but finicky and subject to little things. I wish I had an ultrasonic cleaner.

Day 2: The carb back together, cleaned to within an inch of its life and it started to over flow. I tried different needles, different seats, different floats and it always came out the same. Gas just poured out and then I remembered. I just pushed down the tickle button to open the needle and let the float push it back. Success! The carb dried out and the bike started just fine.

Now on to the next problem. The left side runs fine. The right side loads up and will only run at half throttle and above. I am pretty sure it is electrical since they both run off the same carb. I think I will order two new 12V coils. I need them anyway. Maybe a new set of points wouldn't hurt as well.

To diagnose my right side intermittent firing issue I realize that I have to go back and revisit my ignition timing. I have the 4CA type points plate. It is very crowded with both the condensers and the points in the same space. To make matter worse the points share the same backing plate. The 6CA points assembly have separate plates that will adjust the timing of each point independently of the other set of points. The 4CA set up takes on a Zen like experience as you lose all since of self and time as you adjust the backing plate and try to balance points gap within spec.

I am afraid I just might have been too hasty during my last attempt but they were close.

Thanks for the reply. The wiring from the points to the coil are all renewed since the PO cut the old wires to remove the engine.(He like wise cut the oil lines.)

All connections are clean and good. I am using the original 6V coils which may or may not be an issue but they make spark. I was considering running a single dual plug 12V coil, as wasted spark, but at this stage I may be adding problems.

I have the timing set on both points of the 4CA plate but the gap is a little more open (0.019) on one side and around 0.014 on the other. It may take all my patents but I think I can dial them in if I don't go mad first.

I am not a fan of EI. They are nice but when they are dead they are done. Plus I like the idea of having something to ride in case nuclear war has wiped out most of today's transportation options with EMP.

I set the points gap as the book says. I made a mark on the AAU with a black felt pen for reference. Then I set the points timing. I have a stick marked at 36 degrees BTC. I know where this mark aligns on the plug hole when the other end it resting on the piston crown. I have a flash light I got years ago off the Snap-On truck. It looks like a regular flash light but it has a phone plug in the butt end. Two leads attach here and when I attach one to ground and the other to the points it shows the exact moment the points break at full advance (if I turn the AAU with a pare of ignition pliers that is.)

Using this method I set the timing on both sets of points turning the backing plate for one and adjusting the gap on the second. Then I turned the engine over to compare the points gaps. One gap was a little wide and the other a little tight.I opened the closed one and opened the tight one. Then I set the timing again. I have to say that the gap is now at spec 0.015" on both points and the advance timing is spot on.

After all that I mixed a cup of resin and put another layer of glass fiber on my seat pan. Gotta keep the project moving.

I guess it is to be expected. You get a bike back together out of a bunch of boxes and then you have to make it run right.

The good news is it runs. The bottom end sounds tight and it is pumping a steady stream of oil back to the tank. The bad news is it is not running well. It's running on the left side. It will run on both sides if I crank open the throttle but that side is loading up and quite rich. The plug is wet. The righ side plug is dry and this is a single Monobloc carb model.

I checked the timing and have it as close as I can humanly get it. I checked for a tight valve but they are fine. I checked all my electrical connections and they are good, clean and making good contact.

My thoughts return to the carburetor. It acts like there is still something wrong with the idle circuit because the bike will not run without the throttle cracked.More investigation is in order.

EDIT: I changed the plugs, screwed the idle mixture screw in a half turn and it's better. It runs on both side but it smokes and smells of sunburned gas. The timing still feels slow like it doesn't want to rev. I may have to order the proper tools to time this beast and be done with it. I have it set at 36 degrees BTC but that might be too slow.

EDIT2: I rechecked the timing using the butterfly degree wheel I made. It was a little slow so I fixed that. I started it again and it seemed to run better but it quit. An inspection reveled that a wire had come off the back the the ignition switch. I have put it up for now.

EDIT3: I went back out to the shop and pulled the carb (again) and I think I may still have a stopped up pilot jet. When I sprayed crab cleaner through the low speed jet, I was not getting anything through the tiny hole in the venture. I gave it some more attention and it's better now.

I am thinking of replacing the coil(s) Was also considering using a single 12V dual plug coil and going with a wasted spark set up. That way my kill button would work.

I am pretty sure it is electrical but even the side that is running is running very rich. The left side is running but the plug is wet where as the right side the plug is dry. Very strange for a single carb. I will keep digging.

Yes, I tried two NGKs just for grins but no change.

Something happened Sunday that may have an effect. I was running it and it just quit and I couldn't get it to relight. I quick trace reveled that the power wire had slipped off the spade on the ignition key switch. It may be a question of a bad connection on the power side. I have not had a chance to pull it out of the shop and test this theory yet.

I have decided to make a small, independent wiring harness just for the coils. This is to test the viability of the OEM harness. I have a fuse holder, a toggle switch and wire to each coil. That's it. I want to isolate the original wiring so that I know the running fault is not located there.

The running issues may have been due to a poor connection at the coils. The spades are corroded and when I removed the nut it was clear that there was a great deal of corrosion. The coils did sit outside with the frame for a number of years.

I had a bit of a strange windfall and I came into enough cash to purchase a Wassell Vape electronic ignition system. Ordinarily I would prefer to keep the points but the 4CA is such a poor system and parts it seems are scarce. I could have upgraded to the 6CA points plate and the advance unit but that would cost as much as a EI. I also ordered two new 6V coils.

I did test the electrical and I am getting a good 12V at the white coil power wire.