I've posted a few times sorting out various issues with my once reliable and beloved thunderbird 900. Bike was overheating. Fan Switch is fine and I've had the thermostat out, testing it in a saucepan. It might well have been stuck closed as it seemd to stick when i was testing it but seems ok now. Maybe the bike overheating cooked it? Im leaving the thermostat out of the bike for now just to see whether it stops overheating. However I can't test the bike because it's now running like crap, oiling up the right spark plug. Carbs are a strong possible source of gremlins. Anything else would be worryingly expensive. So I have got em on the bench for a thorough cleaning and a stern talking to. I've messed about with old 2 stroke outboard carbs many times but this is the first time I have grappled with the Tbirds carbs. They came out OK. Leaving the throttle cable on the carb and removing it at the grip was a great tip (thanks Carl Rosner Triumph). I had a problem removing the choke cable, seemingly unable to turn the rounded end tube connector out of it's metal mounting point. Embarrassingly i eventually I had to bend the metal surround. Not ideal. If there is a trick to it I'd love to hear about it. On the bench two of the carbs came apart without issue. The very last screw on the third float bowl is giving me trouble. I'm soaking it with penetrative oil and will have to cut a slot as the cross head has dissolved. I am really hoping not to havr to drill it out. Maybe heat it up with a soldering iron to break the grip? I assume it is possible to buy new screws, but one thing at a time. The carbs intakes, where the black plastic vertical gate comes down, looked pretty grubby but the internals look clean. The inside of the float bowls looked clean. I've bought some liquid carb cleaner (as in not a spray can) and will soak everything once disassembled. It was interesting to read that ultrasonic cleaning isn't always the gold standard it seems to be as the liquid does not get into the narrow passages. I'll be using the carb cleaner and forcing liquid into the channels with a syringe. I was tempted not to touch the idle screw though as I don't want to have to take it to a garage to get it balanced. I know I could count the turns, but perhaps just not touch this part? I need to take the needle and jet bits apart of course. Are there any issues I should watch out for there? I need to check the casting tonight to see whether the carbs are mikuni or keihin carb. What carb kit should I get? I know I should get new gaskets and the little rubber washers. But some kits seem to have needles etc and cost £70 ish. I guess I'll need to inspect the needles I currently have as I disassemble. Can I eye ball a worn needle and jet? The carb rubber manifolds that connect from carb to engine block look a bit ropey . Iinternally they seem fine but I guess it makes sense to replace those now.
I've never attempted carbs myself, but Sprint Manufacturing seems to have lots of bits for the Tbird 900. I've had parts from them for my bike and they always seem good quality.
Thanks. Will have a look. I have been watching a few videos e.g. Superbike Surgery. Poor quality gaskets and o rings seem a common issue so Id rather pay a couple of quid more and not have problems in a few months.
If sprint don't have the bits try nrp-carbs.co.uk. or allensperformance.co.uk If you aren't confident, there's aguy on t300 facebook forum who restores them, think it's Paul Messenger. Sorry it's Paul Burnett.
Ok, I got the last stubborn screw off eventually. Penetrating oil, a slot cut in the head and a bit of persuasion with an impact driver got it off (yes I was gentle). I'm documenting my carb clean journey this as I'm new to this. Perhaps if i make a terrible decision someone could alert me. Thank you. I need to replace the cracked rubber manifolds (carb to engine) and Ill go with Sprint as per advice here. My instinct is to go with the original 30mm diameter rather than the 36mm, which apparently give more top end power at expense of mid range. I'm doing this because as a naked bike she is fast enough for my needs and I do a fair bit of town riding so quite like enough grunt to move the ol girl along. Has anyone got experience of the 36mm? https://www.triumphparts.co.uk/prod...thunderbird-900-cylinder-head-to-carburettor/ Im also buying an o ring kit from Sprint. https://www.triumphparts.co.uk/product/mikuni-carburettor-seal-overhaul-kit/ Assuming all goes well, I will no doubt need to balance the carbs on reinstall. Balancing kits seem to start at £40. https://motorcyclepartswarehouse.co...xs7p1Yv8AqSYaY8eHetxP9YYPmQChnckfgzdCTNCGcDV3 I did see a YouTube video where they used glass bottles. Seemed wonderfully simple and potentially more accurate than a bottom price carb sync kit. Has anyone tried this? Cheers lads.
Thanks for putting up this post, as I previously said, I've never attempted carbs but no doubt will do in the future. I've nothing of use to add but will be watching this thread with interest.
Ultrasonic cleaning is OK if done properly. Many of the cheaper baths are useless noise generators & a lot of the fluids available are snake oil / cheap & aggressive drain cleaner. If the carbs are gummed up or varnished anywhere then it's better to soak them in a bath of carburettor cleaner for a 1-2 days. There is very little you can do to carbs without needing to balance them afterwards, so get a good balancer tool. I find the quality of the dial type gauges is hit n miss, I use a Morgan Carbtune, which hold their value & can easily be sold off for not much less than you paid for 'em. The biggest cause of failure in rebuilding these carbs is an incorrect float height setting. The cage that holds the float is held down by the float bowl & you must mimmick this when setting the heights. You MUST do a bench test for fuel leaks BEFORE re-fitting them back on the bike.
The needle jet & needle do go oval & affect performance. I check the tube for ovality using a digital microscope but you can often get a feel for it by rolling the end of needle around the top. Only EVER use OEM if either of these need replacing. None of the "rebuild kit" manufacturers produce a quality tube or needle & even the dynojet stuff is short lived. You should also check the slide guide for wear. On the side where the slide goes up & down there are wear guides, if this is worn out then chances are the tubes & needles are also. See here : https://store.moto-lab.com/articles/bst36-slide-guide-wear-indicators
