97'Thunderbird 900 cut-out problem

Blacky · May 6, 2016

Went for a ride out yesterday and after about 15 minutes the bike died on me. I first thought it was fuel and opened reserve but would not re-start. There was plenty of fuel in the tank. After about 5 minutes, suddenly fired up, running great for about 5 minutes and then died again. I managed to get back home after about 4 stops with exactly the same problem. This morning it started perfectly as usual and sounded great. Then after a short ride (close to home) and once at temp it started cutting out again. Any Ideas??

crispey · May 6, 2016

I've not experienced this myself but a the air vent for the tank clear, check the fuel cap, remove it and try running the bike. simplest solution. It could be something losing contact through heat, have a look at terminals etc that are in close proximity to engine.
Have a look here

Blacky · May 6, 2016

Cheers. Ill have a check over the weekend. Hope that is all it is??

sprintdave · May 6, 2016

I hope it is something simple too but it could be the ignition sensor, when they start to fail the engine will run until the sensor gets hot, then it cuts out and will not restart until it has cooled again. You start it up, go so far and it cuts out again,over and over.
Also there may be a kink in the fuel pipe or a vacuum problem, I assume you have a prime position on the tap as my Sprint does, if so try running it in this position as that does not use a vacuum,just normal gravity feed. Just do not forget to turn it back onto run position after or you can find fuel seeps into your engine.

stevethegoolie · May 6, 2016

Classic 'crank position sensor' failure. Allegedly!
Engine gets hot - bike stops. Engine cools down - bike starts .... and so on, ad infinitum.
Never experienced it myself (thankfully) yet, but it is not unknown.
A new cps is £39.95 or £49 from Sprint Manufacturing or £39.99 from www.squaredeals-ltd.co.uk plus postage I would assume. Both suppliers seem to be well thought of - I've used both in the past with no problems.

Blacky · May 6, 2016

sprintdave said: ↑

I hope it is something simple too but it could be the ignition sensor, when they start to fail the engine will run until the sensor gets hot, then it cuts out and will not restart until it has cooled again. You start it up, go so far and it cuts out again,over and over.
Also there may be a kink in the fuel pipe or a vacuum problem, I assume you have a prime position on the tap as my Sprint does, if so try running it in this position as that does not use a vacuum,just normal gravity feed. Just do not forget to turn it back onto run position after or you can find fuel seeps into your engine.
Click to expand...

Blacky · May 6, 2016

I am going to check fuel supply as suggested but it seems like the symptoms match exactly to the ignition sensor problem Thanks for the link. Are they easy to fit??

Blacky · May 6, 2016

Just ordered ignition sensor and gasket. Time to study manual before it is delivered next week. I will check other suggestions and let you know the outcome. Cheers for help and advice.

sprintdave · May 7, 2016

Easy to replace, just take off the crankshaft cover on the right side. 1 or 2 screws holds it tight with the correct air gap. The biggest problem is to get the old wire disconnected under the carbs.

Blacky · May 7, 2016

sprintdave said: ↑

Easy to replace, just take off the crankshaft cover on the right side. 1 or 2 screws holds it tight with the correct air gap. The biggest problem is to get the old wire disconnected under the carbs.
Click to expand...

Cheers Ill have a go when it arrives

Havit · May 7, 2016

Hi Blacky , This rings bells with me and my 900 Thunderbird.She run perfect then Spluttered and died. i left her a while and she ran again . Then the same would happen again. Sooooooo fustrating . I checked the filter that was clear plastic and fuel was there . But after the sixth time of cutting out i noticed when i looked at the filter it was filling slowly . When i finaly got her home i removed the petrol tank and removed the petcock to find the filter covered in rust . The inside of the tank had a sludge of rust that was slowing down the fuel feed and reducing and eventually blocking the fuel feed to the carbs . The strange thng was when you stopped it filled the line again. So she would start only to stop again further down the road. I Put the petcock back on and filled the tank full of Cider viniger and left it in for a few days then removed the petcock and empted the tank ( just make sure you get all of it out its not easy as you still hear stuff spashing around when nothing is comming out). You have to shake the hell out of it to get it all out . Then let it dry out either in the sun or an airer. if there is rust particles still in the tank they say use nuts and bolts in the tank and shake it but these tanks are not great to get access into . I used fishing lead shot as they are small and easier to get out. I hope you get your problem sorted i know how fustrating it is when these things happen. The bike is near 20 years old so it could be rust ......Best of luck .

Blacky · May 8, 2016

Wayne Taylor said: ↑

Hi Blacky , This rings bells with me and my 900 Thunderbird.She run perfect then Spluttered and died. i left her a while and she ran again . Then the same would happen again. Sooooooo fustrating . I checked the filter that was clear plastic and fuel was there . But after the sixth time of cutting out i noticed when i looked at the filter it was filling slowly . When i finaly got her home i removed the petrol tank and removed the petcock to find the filter covered in rust . The inside of the tank had a sludge of rust that was slowing down the fuel feed and reducing and eventually blocking the fuel feed to the carbs . The strange thng was when you stopped it filled the line again. So she would start only to stop again further down the road. I Put the petcock back on and filled the tank full of Cider viniger and left it in for a few days then removed the petcock and empted the tank ( just make sure you get all of it out its not easy as you still hear stuff spashing around when nothing is comming out). You have to shake the hell out of it to get it all out . Then let it dry out either in the sun or an airer. if there is rust particles still in the tank they say use nuts and bolts in the tank and shake it but these tanks are not great to get access into . I used fishing lead shot as they are small and easier to get out. I hope you get your problem sorted i know how fustrating it is when these things happen. The bike is near 20 years old so it could be rust ......Best of luck .
Click to expand...

Cheers Wayne, I have disconnected fuel lines and checked flow. seems ok. As you suggested,I have checked for any signs of rust or muck in tank and fuel line and they seem clear. Doesn't have a filter so I think I will fit one while it is in bits.

One of the things you mentioned is that your bike spluttered and died. It seems like with mine, the ignition has been turned off and it cuts out instantly. I now know that the fuel system is ok now,so will try fitting an ignition sensor to rule that out as well. Thanks again

Havit · May 8, 2016

Drain your carb bowls too, just in case theres anything nasty in there , i found a watery substance in mine when i first got her , i make a tin foil bowl to get to the middle screw to stop the petrol going everywhere , worth a try, it least then you can eliminate the fuel side of things

Havit · May 8, 2016

I just hope its not the CDI unit playing up , they can be expensive .

Blacky · May 8, 2016

I know Replaced one 3 years ago. Ouch!!

Blacky · May 11, 2016

Hi. Big Day fingers crossed???. The ignition sensor and new gasket arrived yesterday afternoon and I set about replacing it this morning. Removed RH crankcase cover and the old sensor was clearly visible. The wiring came from the sensor and through the crankcase via a grommet to a connector below the carbs. The wires were quite easily accessible after removing the air filter covers. Two bolts held the sensor in place and it was easily removed. The new sensor was a direct replacement and the socket was a perfect match. I bought a set of metric feeler gauges, as the air gap between the sensor and timing rotor needs to be between 0.6 and 0.8mm. Replaced the crankcase cover with new gasket and fired her up. She started first time and ran like a dream. Replaced the air filter covers, got kitted up and went for a ride. After staying close buy for a few anxious miles without any probs, I realised that the bike was fixed. Rode out for a couple of hours weather great Brilliant!!!!
Thank you for all of the advice> I would not have had a clue without your help.

Havit · May 12, 2016

Nice one, great stuff, glad you put up photos.

Blacky · May 12, 2016

Yes they are torx bolts holding the sensor in place and yep, looking forward to a hopefully problem free summer. Cheers

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