Thunderbird 900 Spitting Out Its Coolant

Had another coolant explosion yesterday.
Riding the bike fairly hard, through stop go London traffic.
Splosh marks all over the engine where it has, I assume, got hot and boiled out of either the coolant cap or the reservoir.

The fan does come on but I am wondering if it is coming on too late.
I have ordered a new thermo fan switch. Based on other posts I think this non triumph part should fit. https://www.ebay.co.uk/itm/276516898011

The bike has been reliable for years but has now got gremlins.

The green neutral light is not coming on, but this only happens when the engine is hot. I have read the other posts and will check the wire connector to see if it is corroded.

The engine was only starting on 2 cylinders. I replaced all 3 plugs a couple of weeks ago which fixed things. The right one was oily.

New plugs worked wonders but now the problem is back with a vengeance and its only been a couple of weeks.

What is causing that plug to oil up i wonder?

I am worried now that that the valves might need work, which I am not confident to do.

I am going to look at the air box today. I noticed the plastic collars that mount the box to the carbs and the carbs to the engine looked a bit worse for the wear.

I guess the carbs might have gummed up. I have had that often enough on my 2 stroke outboards. I could probably manage removal and cleaning, but it is not a 5 minute job.

I cant see a link between the coolant issue and these new symptoms, but I am happy to be educated.

Bike has done over 30k miles now. Kept under a pram cover thing. Battery new ish and well looked after.

Right, I am off to take the bike to bits. Sorry about the endless open ended questions.

 

Are you thinking worn cylinders? If that is the likely diagnosis I might just hand it over to a mechanic that knows what they're doing.

 

I have a horrible feeling it's a cylinder or valve issue but I guess it could be gummed carbs. I'm not confident to tackle valves etc but I've sorted many an outboard carb so could probably manage the triumph. I've bought a compression tester and will do my due diligence.

 

This is at the edge of my knowledge, but the fouled plug and coolant boiling issue suggest a cylinder issue to me. She doesn't seem to be burning oil though.

 

No I did not. I thought flushing the radiator had solved the problem but definitely not. I will do a compression test before buying a new cap but thanks for that very useful tip.

 

Ok, the results are in!

L cylinder 12 bar = 175 psi
Middle cylinder 12.1 bar = 180 psi
R cylinder 13 bar = 190 psi

I do not know what the compression readings should be, but seeing they are fairly even seems positive, does it not?

I am noticing some black gunk around the air intake of the right cylinder.

I did try to buy a new fan temp switch but the one i ordered did not fit.
I will look at a new radiator cap, but am sceptical that this is the issue.

Maybe airbox is gunked up?
Maybe all that black crap means the carbs are also gunked.

Had the compression test shown wildly differing results I would have taken her into the garage. However, I am not sure what the next step is. Probably, look at the air filter and box.

BTW I have no idea what a wet test and a dry test means. Will have to google it.

 

I put a new plug I had lying around in the right cylinder after I did the compression test. Rode to work today. Started and ran well. Reluctant to start this afternoon, but ok once on 3 cylinders. Then spat out the coolant again half way home.

Maybe an airbox or vac pipe would explain some of the symptoms (maybe). But the overheating thing concerns me. Could be an unrelated issue I spose.

I think it is time for the pro's to take over frankly.

 

I am working on the basis that if I rule out some things before I take it in, I might save a few quid, and learn a thing or two along the way.

so i finally got round to testing the fan switch in hot water. Connection made at 95 degrees. Haynes says its 100 degrees. So not the problem.

I then removed the thermostat and did the saucepan test. Seemed to stick but it did opened at 85 degrees.

Do they stick? Seems possible, but not much to go wrong.

Next step is to take closer look at the water pump.

 

Engine starting rough so I have not had a chance to see whether the thermostat is the source of the overheating issue. I spoke to Carl Rosner Triumph in Croydon. Amazing guys who were full of helpful advice. Most likely issue with oily plug is sticky carbs. I am going to remove them and try cleaning myself. If that does not work I will take the carbs in to Carl Rosner's to have them cleaned by pro's with all the right gear.

 

Was all going well until the last bl***dy screw. Properly seized. Cross head now mashed. Those videos never show the pain of getting the part apart. But thanks