T100 Splutters When Hot

Shit in the carbs, otherwise one of the key electrical components breaking up, crank sensor, coils or ecu

 

If I understand you correctly enriching the mixture cures the sputtering?

Year? Mileage?

The reason I ask is because it suggests a fuelling problem not an electrical one. Meanwhile I have a good pal in The Borough. Used to live in Wilton myself.

 

Richard Batchelor
Welcome to the family. Check you haven't got some water in the fuel. Or damaged a inlet hose or something or trapped a fuel pipe or something.
Regards
Joe.

 

On such a low mileage/aged bike I suspect a mix of tank rust particles and varnish from dried fuel have built up in jets and galleries. Also, the little rubber vacuum caps on the inlet manifolds may well be perished and leaking leaning out the mixture.

You really need to dismantle and clean the lot but for starters I would blast everything backwards with a carb cleaner aerosol. How mechanically minded are you?

 

From Downton?

 

once a month, helps to keep it regular....

 

I tend to agree with this line of thinking. I own three Hinckley Triumphs. Two of them I have had to replace the ignition coils. When they get warm they start breaking down. The ignition pickup can also do this,.but I have had particular problems with coils. My thinking is.that if it were a fuel problem it would do it.all the time, not just when it were warm. By choking the engine you make it richer which makes it easier for a weak ignition to ignite the fuel. Let us know what.you find. That way we all learn from your experience. ...J.D.

 

Ok. Buy the Haynes manual and see if you have the confidence to do a fairly simple job in bite size chunks.

At the very least, fuel tap off, fully unscrew the Allen screw in the bottom of each float bowl with kitchen paper underneath and see what crud emerges. Then re-install.

It is of a fiddle than complicated but the four screws holding the float bowls are accessed from underneath and soft metal, easily burred.......

 

I don’t materially dissent. I have had similar issues AND crud in the carbs simultaneously. Cleaning the fuel lines and jets improved but did not cure the problem. My ignition coil misfired below 3k rpm within minutes of startup but a rich red ‘soil’ of rust particles in the float bowls got sucked up at higher rpm. Both needed addressing.

 

Well,.I guess we'll know when the man fixes the problem. ...J.D.

 

Richard,

Not knowing your skills/knowledge I don’t want to insult your intelligence! However, it strikes me you have 2 options:
Self help or
Local dealer
For the latter I would suggest an independent repair oriented outfit rather than a franchised outfit with high overheads.

Testing and fitting a new ignition coil is relative child’s play. You need a £10 multimeter, a Posi screwdriver, 10mm spanner and pliers......
The coil is just accessible to multimeter probes on the frame at the front of the tank. Read the multimeter ‘destructions’!

• Secondary resistance. Remove both plug caps and measure the resistance between them. It should be about 15kΩ. If it is too high, pull the plug leads out of the coil and measure directly across the coil contacts. If this reading is ok, you have a bad plug lead.
• Measure the resistance between one plug cap and the engine. It should be infinite.
• Primary resistance - pull off the two small leads feeding the coil and measure the resistance between these two terminals of the coil - should be about 6Ω.

You need to lift the tank to actually replace the coil. Simple enough.

The other coil to test is under the RH triangular side cover. It is the pick up coil that triggers each ignition. Follow the wire exiting the rear of the triangular sidecover up under the (removed) sidecover. Adjacent to the battery you will find a small 2 pin connector. You should get about 570 ohms resistance there.

The tests are not infallible given the nature of the coil. If it IS one of the two coils they are ultrafine wire windings that break. As they start to go off the heat expansion opens and closes the break until they fail totally.

The pickup coil is OEM only (£57) and available online.
https://www.fowlersparts.co.uk/parts/view/T1290131
You will need a £5 T1260968 gasket too. Plenty of ‘how to’ stuff online.

The ignition coil is best replaced with the 70506 PVL item (£50) used on older BMW twins. https://www.motobins.co.uk/

Let us know how you get on.

 

exactly the problems with my bonnie, had the carbs cleaned and new jets and float valves installed but it was still conking out, changed the crank sensor and coils and in the end the ecu which fixed it, a mix of more than one problem all of which needed sorting