Don't kill me...Triumph sounds a little sick...diagnosis??

My TR6R is only firing steadily on the left cylinder. Both sides have the same compression and leak down test results, it has electronic ignition so if one side fires, the other has to as well, and I just rebuilt the carbs (it has a bonneville head) and the push rods are straight. What could it be...is it a bad cam lobe?

 

Have you confirmed that there IS spark through the plug itself?

If there is in-fact spark to the sick cylinder and as you say, you "just rebuilt the carbs," I would start there - no plugged pilot jet, clip in same position on needle as the healthy side. Slide works properly, good seal around boot - no airleak, etc.

If you do have spark and the carb is providing proper fuel mix, then possibly it is a lobe. Remove valve cover and turn it over while having a look - Do the valves from the right side seem to operate just as much as the left?

If so, it should at least fire even if the lobe is going a bit flat?

When you say "only runs steadily on the left cylinder" do you mean the right does not fire at all, or just not very well?

 

Could be as simple as a bad wire. Make sure that you are actually getting spark to both sides.

Always start with the simple stuff.

 

If it was a bad cam lobe you would be hearing the push rods going nuts, and the compression wouldn't be the same. Is there a fouled plug? Perhaps a bad plug wire?

 

try switching your plug wires side for side. could be a bad coil, and they can seem ok at low rpm's but peter out when needed to fire a tight charge.

if you had a flat cam lobe you could tell by pulling the rocker box covers.

 

Coils?...could be bad....maybe volt not transferring through.....

 

I've switched plugs from side to side as well as wires with no difference. The way I wired up the ignition it has to fire on both sides equally (at least thats what the manual said). It no longer uses one coil for each side, they now fire at the same time for each cylinder. The carbs are 100% clean and tight with new jets and seals. When it was running there was no excessive rattling so I guess it's not the cam lobes? Oh well, I'm gonna tear it down anyway, I just was gonna see if there was anything in particular that I should look for. Thanks for all the help guys
Jake

 

Another question...what size Mikunis do people use on Triumph 650 twins?

 

what year? i had poor running 56'.turn out that the early bolt togeter crank was comming apart. when did the one pice crank come out? anybody know?

 

Mine is a 70...so that probably isn't the issue...thanks though

 

both plugs fire at the same time...?

How does that werk....?
Aint they fighting each other?

(ignore this if it's dumb...)

 

Its not that both plugs fire at the same time, both coils fire to each plug...does that help?

 

Ahh..got yah.

Sowwy.

Good luck with it!

Cheers
MAIKI

 

So your running wasted spark?

How old is the electro ignition? That could very well be faulty. Is it a Boyer digital?

Ruled out valve clearance? Carb sync?

 

wasted spark? I don't know, I wired the ignition exactly like it said to for the components I have. The ignition is a Boyer and it is brand new. I'm pretty sure the problem is not ignition. It has spark, I've checked that several differend ways. By valve clearence do you mean the slop between the rocker and the valve? If so, its no different on that side than the other...I didn't sync the carbs, but I tried to adjust them the way it says to in the manual...ie...take off one plug wire and adjust the other cylinder..ect..but if it only runs on one cylinder it's hard to adjust the other one...

 

Sorry....I was just going down the line. More for in my head than anything. Its hard to do diagnosis over the net, but sounds like your all straight. Boy that's a doozie. I had a similar problem on my one Beezer, but that was a vacuum discrepancy in the carb, and it was only single carb. The peculiar thing was it only affected the left carb. Same as if you ever happen to run outta gas. You know it because that left carb just quits firing bfore the the right is affected.

You got my best wishes on that one....

If I happen to find anything additional I'll flow it your way

 

Just an FYI for those that don't know...both pistons in Triumph twins rise and fall at the same time. Just like a single, but there are two pistons. Both cylinders should fire at exactly the same time.

Wish I could help you, Jake...I have a hard enough time trying to figure out my Triumphs.

By the way, I have Boyer ignition on both of my bikes, and they both have a pair of 6v coils to fire the plugs. Is this not how yours is set up?

 

hey ol scratch...explain a little more about the left cylinder not firing when you run out of gas....the left cyclinder is the one that won't fire on my bike. I know I had enough gas, but maybe it's something along those lines...I don't know, I'm confused....my trail 90 never gives me problems like these

 

Triumph cam lobes are nitride hardened startin sometime in late 70 and never go bad

OK- bet ya it's fuel.
Why did the carbs need rebuilding? Bad gas infestation from sittin too long?
When you clean them use guitar string, solvent, compressed air to clean ALL of the circuit passages.
Can really trick ya, sounding and feeling like ignition...but most of the time it's fuel delivery.
Some of the components of modern pump fuel are real resistant to solvents, thorough job cleanin is real important.
Good luck man

 

Yeah, the carbs were hella gummed up. I'll try to clean em again, but I just bid on some mikunis on ebay that I think will be better anyway...I was once told by an old flat tracker that the only thing worse than an amal is two of them...

 

[ QUOTE ]
Both cylinders should fire at exactly the same time.


[/ QUOTE ] i dont think so. my mag(56' tr6) fired one at a time. if they fired and the same time it well as been a single.-josh

 

Electronic ignition equipped brit bikes fire both cylinders at the same time, but not on the same cycle. When one piston is on the compression stroke, the other is on the exhaust stroke. Most lawnmower engines also fire on the exhaust stroke, it serves no purpose but it's a simpler set up.

Stock dual points equipped bikes fire one cylinder at a time.

When converting to electronic, it's important to switch from 12v to 6v coils, since the new set-up will run the coils in series. This way, you can keep the resistance as it should be.

Hope that helps.

 

What he is saying is that both plugs fire at the same time, but the cylinders are 180 degrees apart as far as the cycle goes...when both pistons are at top dead center, one has just ignited and is fixin to do its power stroke while the other has just pushed out the exhaust and is about to do its intake stroke...is that better...
As far as the ignition goes...I don't remember what I did exactly, its confusing for a colorblind kid to do wiring anyway...but I do remember I fallowed the boyer diagram that was provided and double checked it with the triumph diagram....but I don't remember about the coils...I used the stock ones...would those have been 12V or 6V on a '70 TR6?

 

Before buying more carbs, you might swap the anals from side to side. If the problem transfers to the other side, you've narrowed it down to them.

If not, then you know that buying more won't fix it.

 

Also, this reminds me of a friend's twin from years back which he brought to me running crappy. The problem turned out to be that in one carb, the needle/clip was on top of the retainer plate instead of under it and therefore was free to jump up and down in the jet.

 

Worn out Mikunis are just as bad as worn out Amals.
You can have the Concentrics sleeved for $50 so they'll last.
I've run Concentrics, Monoblocs, Mikunis, and magnesium bodiy Kiehen flat slides on my Bonnies and the Concentrics are a good street carb when they are in good condition.
If your Amal bodies aren't worn oval you can get a pair of new slides for less that the cost of used Mikunis. Also if you run the Mikunis where ya gonna get correct jetting and set up info?
Yeah I'm a die hard Brit guy.

 

You say it`s a TR6R?That`s a 650 Tiger single carb.
Someone must of swapped it.
I have a sweet `70 TR6R.You might want to change back to
a single carb they are more reliable and easier to tune.
IMO stay away from Mikunis,Nothing wrong with Amals,unless
they are worn out.A new one is around 100 or you can get
it reslieved($50.).A rebuild kit is under $10.
I suspect your problem is in the carb.
Always the first thing to do is pull your plugs.I bet the one(or both)are fouled sooty from too much gas.
Take off the carbs and soak them in carb clear(take out
idle adj valve and rubber O ring first)Check float and f
valve.replace valve with vitron tip one.
Then blow out carb body with air,you might need to clear idle passages with a wire.
When you pull the bowel off make sure the main jet holder is tight.They caused me alot of grief on a long ride.
Also ,like someone else said,check the needle to make sure the figure 8 clip is in place(same groove in both carbs)
and the clip isn`t caught up in the spring.

I`m also running a Boyer they are great(as long as the battery is good).Did you strobe it after you got it running?
The couple I seen,if you just relie on the white dot you
will be a little retared.The dots are OK for static timing
but you need to stobe it.The `70s are easy,they have mark
on the rotor.
Another thing someone else said,you need 6volt coils or
a double lead coil,a early Harley or aftermarket,you need low resistance.Your stock coils are 12v.It makes a big differance.
Put in new plug NGK B6ES.Keep checking them,they tell the
whole stort.
I also sugest when you change coils to replace the leads
(plug wires) use solid core.(unless you got the newer digital Boyer) go over all your connections for tightness,
especially the + grounds(run one to the motor,a rocker stud)

After you get it all sorted out,you might want to gear it
higher.I did mine and it made a trimendous improvement.
With stock 19 tooth drive and 46t rear sprockett(stock for
`70 650s)it really sucked on the freeway at 55mph I was
turning 4grand and with the vibration I had a hard time
staying on plus I couldn`t keep up and was almost getting
run over.
First I went to 20 drive and it made a big differance,then
I changed the rear to 43tooth and it feels like an easyboy
recliner at 75.It still has plenty of pep on the take off.
If you go to a 21 tooth drive(the biggest that fits after a little metal removing)you will be smiling.There is a Tee shirt that says,Ride a Triumph and become a mechanic...
That`s part of the charm of these babys,I love tickering
on it as much as I love riding it!

Good Luck...JR

 

Just read Disatrons post,agree intirely on the concentics.
Had to add,make sure you don`t over tighten them!
That can warp the shit out of the body and your slides
will stick and leak.You might want to put a kill switch
on it too,but that`s another story.
JR...

 

Hey that's good info about sprocket sizes JR. That was something I've been curious about.

I'm in the process of re-doing my chopper right now and was considering changing the sprockets because when it was together before it would buzz like crazy at 60 mph and anything over. It threw a rod last year at about 60 or so.

I found a '71 bottom end to replace the broken cases and my big bore kit just came in the mail today. Got it down to the bare frame this weekend and just finished all the molding and filled a lot of unnecessary holes.

Oh yeah, thanks for elaborating on the firing Jake. I guess I could have been a little clearer. Good luck!

 

Hi Bass,
Did you get your bb kit from MAP?
They are great,I just put in new MAP clutch plates.
Love them ,also running a MAP oil filter.
Definately put a 21 tooth grear in(about 30 bucks,on e-bay
often)
Was really impressed by the bb kit a friend just in a `69
Bonnie,he used thier belt drive primary kit too.
He`s got a fortune in that bike.

Good Luck...JR...

PS...MAP also sells a Mikuni kit,they can keep it...:]