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#555024 - 07/26/14 3:53 pm Overheating T140V  
Joined: Jul 2014
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HST Doctor Offline
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England
Any ideas or help on this one would be welcome.

I took a chance and bought a tidy looking bike off eBay without seeing it, it is tidy and has been rebuilt with new carbs etc. After it was delivered I couldn't set up the idling and found that one of the carbs had the blanking plug for the idle jet chamber missing, I got one for pence from AMAL, fitted it and bike ran OK.

I have not had much chance to get out on the bike, but took it out Thursday and within 20 minutes of riding it in traffic, it was cutting out - it would only run when stood still by blipping throttle onto main jets. It was OK when riding with throttle open, until there were a few rattles and squeaks from the engine.

The carbs were very hot and it is fairly obvious that the fuel was evaporating when on idle.

The most alarming thing was that the engine oil had been full, but was just touching the bottom of the dipstick when I got back, there was a strong scavenge return into the tank, so whilst I haven't had chance to drain sump and check amount in there, I don't think it was wet sumping.

I had previously set up the carbs and checked the tappets, all OK, I haven't checked the ignition timing, its electronic, but it starts and runs well I can't see that being far out, although I will check it. I have checked both cylinders compression, they were both 100psi.

I am going to change the oil before I run it again, as I feel,it got so hot and with the bare minimum or less in the tank, the oil must have suffered.

Any advice on what may cause such overheating would be welcome, the ambient temperature on the day it happened would be high 20'sC. As the weather remains good here at the moment, the bike is unrideable with the current fault.

I have owned two other OIF Bonnies 30 odd years ago and never came across this problem.

Last edited by HST Doctor; 07/26/14 3:57 pm.
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#555036 - 07/26/14 4:57 pm Re: Overheating T140V [Re: HST Doctor]  
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HawaiianTiger Online content
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Maui Hawaii
I think you are trying to run a fresh motor as if it was already broken in. Low compression, loss of oil, not running right, running hot, all things that might be considered normal on a new motor.

You are doing the right thing by checking the settings of everything, but really, you must verify that the timing is SPOT ON, not just close. Well, several degrees retarded from normal will be OK.

A freshly rebuilt motor might be expected to run hot, due to several factors, but it's the heat that kills, so short hops may be what you need until you can run it without over-heating. I like to run a little richer that stock settings for several hundred miles. You are loosing some incoming charge past the unseated rings anyway. One notch on the needle richer is usually enough.

Change your oil frequently. It's getting ruined by heat and gas contamination.

I'm not a OIF expert(if I'm an expert at anything) but if your carbs are getting heat soaked, then you may need insulating blocks between the carbs and manifolds. However, if that is the case, your bike would be a right b*tch to start from hot.

Cheers,
Bill

Come to think of it, the carbs on the 750 are pretty well insulated from the manifold by virtue of their having fat O rings and the shouldered mounting bolts that when properly assembled do not allow the carbs to come in contact with the manifolds. Check to see if the carbs can be moved about a little. They are essentially rubber mounted.....

Last edited by HawaiianTiger; 07/26/14 5:00 pm.

Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Flying Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
#555052 - 07/26/14 7:16 pm Re: Overheating T140V [Re: HST Doctor]  
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Excalibur Online content
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Congrats on buying a bike and getting out there and riding it.
There can be a lot of sorting out with bikes that have had previous owner/s tinkering and with all due respect you've really got to approach the task with the view that they knew nothing. Problems can be heaped on top of problems and it can take weeks to weed out all the issues. Consider it a labor of love and all will be well.

'Carb blanking was missing'. If there was something missing, replacing it fixes it then you'd just have to wonder what else is wrong. There's lots of threads on carb set up,, float level, idle jet cleaning, insulator blocks, etc. Lots of snippets of info that weren't commonly known 30years ago too.

Drain the crankcase, measure the quantity and check all the strainers. Being a previous Bonnie owner you'll be aware that the crankcase strainer should be cleaned spotless else particles can upset the scavenge pump. I suggest solvent wash and air blast.

Definitely check the timing before riding again. I think consensus is to run a couple of degrees less max advance for todays' fuel.

#555053 - 07/26/14 7:17 pm Re: Overheating T140V [Re: HST Doctor]  
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downhere Offline
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Timing retarded.

#555064 - 07/26/14 8:04 pm Re: Overheating T140V [Re: HST Doctor]  
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"carbs were very hot".carburetor insulators installed? what did the plugs look like?
joe

#555070 - 07/26/14 8:53 pm Re: Overheating T140V [Re: HST Doctor]  
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Pete R - R.I.P. Offline
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Pete R - R.I.P.  Offline
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Vic. Australia
You shouldn't have insulator blocks on T140 carbs. The O-ring on the carb flange should be the 0.100" thick Triumph O-ring, not the thin AMAL O-ring. There should be about 0.050" air gap between the flanges, when the O-ring is lightly compressed. That'll keep the carbs cool better than any insulator block.

Check the timing at full advance with a timing light, and check both cylinders. Rev the engine enough that it stops advancing. If it's the slightest bit advanced, it can cause you trouble with capital T. A few degrees retarded (that's about 0.075" at the rotor circumference) won't cause any problem.

#555109 - 07/27/14 3:27 am Re: Overheating T140V [Re: HST Doctor]  
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I'm curios if it has AMAL concentrics? If so, I'm not aware of any using idle jets. You say T140V. What year please?

Is it a Boyer ignition?

Also, when you did your compression check, did you have the throttle wide open during kicking?

When you adjusted valves, engine was stone cold right? Low compression could be a result of tight valves.

And look for air intake leak as well by spraying a mist of water while the engine is running at the carby base where the o-rings are and, where the 2 mounting nuts and o-rings should be.

Is the carb intake crossover tube in place?

Oh, make sure your charging system is working and you have a known good battery.

#555116 - 07/27/14 5:01 am Re: Overheating T140V [Re: HST Doctor]  
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750Bonny Online content
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Takasaki, Japan
It's been 37deg C here the past few days! I have got my bikes sorted so they can handle the temps out here.
Strobe the timing and set it a couple of degrees retarded. 36deg BTDC
Have you had a look at the plugs? colour?
Check you have decent fuel flow into the carbs
Make sure you have the correct 'O' rings as suggested, the carbs should have a bit of wobble.
Check you have absolutely no air leaks, fit a new snug fitting balance pipe.
What size jets are fitted. I have 200 mains and 107 pilots, needle in bottom groove.
I think modern fuel doesn't have enough petrol in it for old bikes wink
Incorrect timing ,Weak mixture = overheating
Make sure you put the correct type of oil in. Think about fitting and external oil filter like the spin on Norton type.
Get out and enjoy the weather while it lasts!


Triumph Bonneville T140v 1977
Triumph T120R 1971
Englishman in Japan
#555348 - 07/28/14 2:22 pm Re: Overheating T140V [Re: HST Doctor]  
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HST Doctor Offline
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England
Thanks for the replies.

I had a couple of hours this morning, so started with the basics, I pulled the plugs, RH was black and sooty, LH was wet and sticky, also black. The LH carb had some residue in it as well.

I have stripped the carbs and re checked the float heights, connecting each bowl to the fuel line to get the same fuel level in each bowl.

I have got very thin gaskets between the heads and the aluminium manifolds, so have ordered some of the correct thick, insulating gaskets, along with new carb-inlet manifold 'O' rings. The Triumph part number corresponds with an AMAL No. so I'll see what thickness ones turn up, the ones in there are more like 0.065" than 0.100" dia. The carbs were tight to the inlet manifolds, so I have ordered the correct locking nuts for the carb-manifold studs (they were just plain nuts nipped up tight).

The next stage will be change the oil when it arrives (couldn't source any decent classic 20/50 locally), fit the new gaskets and carbs, then time it up. I had Champion spark plugs in, but have now fitted NGK to see if they are an improvement. Once it is running I will put a meter on and check the alternator output. I assume its best to check timing from both coil outputs, to eliminate any issues with a coil or HT side of things, as this should show it up.

If someone could spare the time to explain setting up/checking/timing the Boyer ignition system I would be grateful, as I have only previously had points or a Lucas Rita system - and that was in 1978/9 before I got side tracked by Harleys.

Some other answers: Yes, balance pipe fitted between inlet manifolds. Compression was checked with throttle closed. Engine was stonecold when tappets set.

#555363 - 07/28/14 3:29 pm Re: Overheating T140V [Re: HST Doctor]  
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HawaiianTiger Online content
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Maui Hawaii
Sounds like you'll have it sorted in no time.

I like Champions, but the NGK's seem to work better during break-in since they don't seem to foul as easily.

Cruel as it seems, you need to rev your motor to 5000 rpm while strobe timing. 36-38 degrees advance max at that rpm. Depends on the quality of your fuel, mostly.

Spark plug checks in the first miles of a break in are pretty hopeless. Black and sooty with some oil is not uncommon. Trust on you other senses to give some feedback on how it's running. You can get mis-information from your timing light and your plugs aren't much help.

How does it run? Smell hot? Any pinging? Easy to start? Easy to start when hot? If it's all right, the bike will run like normal but may get hot if run too long. There might be a bit of smoke from the exhaust until the rings seat.

Let us know how it goes. Try a compression test hot with throttle full open for best results.

Cheers,
Bill


Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Flying Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
#555415 - 07/28/14 7:16 pm Re: Overheating T140V [Re: HST Doctor]  
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John Healy Online content
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Try blippin the throttle so that it momentarily reaches 5,000.


#555481 - 07/29/14 2:23 am Re: Overheating T140V [Re: HST Doctor]  
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L.A.B. Online content
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Norfolk, UK
Originally Posted By: HST Doctor
If someone could spare the time to explain setting up/checking/timing the Boyer ignition system


http://www.boyerbransden.com/instructions.html

#555529 - 07/29/14 10:39 am Re: Overheating T140V [Re: HST Doctor]  
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Last edited by 750Bonny; 07/29/14 10:46 am.

Triumph Bonneville T140v 1977
Triumph T120R 1971
Englishman in Japan
#555583 - 07/29/14 6:04 pm Re: Overheating T140V [Re: HST Doctor]  
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Pete J 77T140 Offline
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Stow, MA
My t140 overheated with similar symptoms when the flanged studs which serve as both the bolts holding the intake manifolds to the head and the mounting posts for the carbs were loose - allowing an air leak in the intakes. Given the incorrect nuts and flush tightening you mention on these there may be more that's incorrectly done in that area. Those studs need to be double nutted with loctite into the head - on mine they are prone to vibrate loose. Gasket sealers don't work well on the intake manifold gaskets because they're gas soaked.

The water test alluded to above can be used to test for an air leak there. I've also heard of people using an unlit propane torch to see if any propane gets sucked in thru the air leak -- but that sounds dangerous.

Also check the hole for the choke mounting bolt - if you have one -- it's a common source for air leaks and the threads may be stripped.

#559453 - 08/22/14 3:23 am Re: Overheating T140V [Re: HST Doctor]  
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HST Doctor Offline
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England
Thought I'd post an update on this.

I stripped the carbs and fitted the 'stay up' floats, the float heights were way too low, so i have set them correctly. I removed the inlet manifold studs, one of which wasn't tight and refitted them, using a slightly thicker gasket (70-2968, in place of 70-5660) new carb o rings and the correct lock nuts.

I replaced the Champion spark plugs with NGK and changed the oil, using a classic 20/50, I strobed the bike, the timing mark is not visible at idle, but at 5,500 rpm it is right on the pointer.

I haven't had time to take it for a proper ride yet, but just riding it locally, it has improved massively, it is idling better (sometimes used to cut out when it was idling, whether it was cold or hot), it is pulling better, just like I remember a Bonnie should and my neighbour commented on how good it sounds (it has pea shooters fitted).

So thanks very much to those who offered advice, no doubt I will be back for some more.

Actually I have a couple more questions, what idle speed is best to set the bike at?

And, my bike is fitted with K&N air filters, all the original air box is not there and wasn't supplied with the bike, any opinions on whether its best to stay with the K&N's or get hold of an original air box. The K&N's slightly foul the side panels, making it difficult to fit them, so I may have to get hold of another pair and modify them, unless I go down the original route.

Last edited by HST Doctor; 08/22/14 3:25 am.
#559469 - 08/22/14 5:59 am Re: Overheating T140V [Re: HST Doctor]  
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UK Berks
Where the heck are you in the uk that you can't get 20/50!?

I assume that you have retro side panels fitted? They can look better than the boxy original- a matter of taste.
Loads of bikes run with K&N so maybe fiddle with the alignment? Or fit the round type retro filters

#559479 - 08/22/14 7:02 am Re: Overheating T140V [Re: AngloBike]  
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HST Doctor Offline
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Originally Posted By: AngloBike
Where the heck are you in the uk that you can't get 20/50!?

I assume that you have retro side panels fitted? They can look better than the boxy original- a matter of taste.
Loads of bikes run with K&N so maybe fiddle with the alignment? Or fit the round type retro filters


I think the side panels are original, it's tricky to get the top spring on with the K&N's in place.

#559493 - 08/22/14 8:06 am Re: Overheating T140V [Re: HST Doctor]  
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Wow.
Didn't realise that it was even possible to fit K&N's with the air box.
You could google youtube's Lunmad videos where he makes some side panels out of a baking sheet to replace the original plastic ones.
You could buy a set of earlier ones that are
Made of cast alloy and cut them about in some way. But I don't know what the situation would be if you wanted to refit the plastic covers. The bikes look pretty good if the cast covers Are polished up or the steel inner and cast inner are painted the same colour as the tank

http://m.youtube.com/watch?v=Ooj9zFLc4nc

#559495 - 08/22/14 8:24 am Re: Overheating T140V [Re: HST Doctor]  
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HST Doctor Offline
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England
There is no air box, the panels look exactly the same as the ones in the parts manual, so i am assuming they are original, the bike is red/ black, but where fitting the springs is awkward, the paint is slightly scratched and the panels were thr original blue colour.

I think I could modify the existing panels, but would rather buy another pair to do that and keep the originals, I will look out for a complete air box assy as well, in case I want to put the bike back to original.

I will have a look at the video's thanks for the info. I'm a bit rusty on these, as I had one in 1978, but got rid in 1980 and had harleys ever since, until buying this one a few months back.

#559500 - 08/22/14 8:46 am Re: Overheating T140V [Re: HST Doctor]  
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So you still have the outers but no inners?

If it was me I'd buy some retro side panels that make the bike look er... More retro.
Gives a 60's look.

But buy decent ones as some are flimsy and don't come with fittings whereas others are quality and come finished and with fixings. Can't help with suppliers but try LPWilliams

Or maybe you could cut a set of original outers about and find some way of spacing them apart a bit more but the ideal bonnie has a wasp waist that the OIF air box kind of ruins IMHO

#559503 - 08/22/14 9:07 am Re: Overheating T140V [Re: HST Doctor]  
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HST Doctor Offline
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The outer panels, plastic with the Bonneville 750 name plate on. Nothing remains of the air box, the previous owner has made two brackets that the side panels butt up against in the middle.

It's not urgent, but something I will play around with, l will get hold of some other panels and see what can be done..

#559860 - 08/24/14 5:59 am Re: Overheating T140V [Re: HST Doctor]  
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sucking air


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