ST4S - Soul destroying issues of getting it to start


So an update after a bloody good thrash on the st4s today, a good 160 ish miles covered in Wales and Shropshire (fuel limited as I wasn't stopping!). I think I used 6th once and she definitely goes like a train and sticks like my 748 to the road in the corners. Absolutely cracking piece of kit. Downside, my 12 year old son and his stomach...

Son: "Dad, can we stop for lunch on the way?".....

Me: "Nope nope and nope. Get your bacon and egg sarnie in you and get on the bike as I don't know if it will start again when hot"

Son:"but dad, we are going out over lunch and I'll get hungry and you said about dinky's"

Me: "get scoffing and get on the bike I've changed my mind 🤦"

Needless to say he was not best pleased he was missing his hobbit style eating menu. When we got home he stood there when the engine was turned off and said "dad, that Duc is awesome. As comfortable as the ST2 and goes like the 748, can we do that again? "

I think I have a not so mini me in the making 😊

Hope you all have a cracking weekend


Evening all,

A small update on the ST4S after a week or so. She was still being an absolute tw*t at starting, especially when cold. Sometimes yes, most of the time no. Needless to say muchos cussing in the garage. I was either thinking sprag, starter or ecu (the latter being more preferable)

In conversation with ChrisW, he pointed me at a replacement ECU on the Bay of E for the bluestreak one I had, he sent his address for me to send it to for some dark voodoo and it arrived back this lunchtime. This evening I went through the usual pain for fairing removal (getting well versed at that), nice easy ecu swap, reconnect everything, remove airbox lid, turn the key and boom. Alive in three chugs (as i say for my st2) with the DP exhausts on!!!!! Bet my neighbours thought i was mad having a little jig on the drive with a tin of ale in my hand.

Mentions of the TPS have been made, but thats after the next service. I am now going to put some miles on it (it only has 8300 after 20 years) and fit the panniers to it (bloody bolt holes are a mil or so out so I cant get them in!. Thats the next job (on another thread).

Many thanks to everyone for your help, certainly a learning curve and if anyone is coming through Shropshire (Much Wenlock) please come and pop by. The beer is always cold and the braai always lit.

A very happy Keith (and 12yo son!)


New member
Ever so glad you seem to have nailed it ....... that Chris is frighteningly good, isn't he?

However, if you get any more intermittent starting problems do take a look at the Crank Position sensor. I once had a complete refusal and went through all the usual, fuel filter etc, to no avail.

Eventually decided on the CPS and went to order the correct Fiat Tipo part, which meant checking the connector into the loom ..... so I tracked it down, broke it and compared to the picture of the Fiat part. Stuck it back together again, thought I'd just try the starter buttom and boom, immediate start up.

I've had a few times when it's not wanted to start, usually outside a pub when the entire beer garden is watching, and giving the CPS connector plug a wiggle does the trick.

You might want to clean the starter motor out sometime too, they get full of dust and shit.

And you're right, they make brilliant undrcover sports bikes .... even better with a large topbox stuck on the pillion seat, that really upsets the Pantigirdle brigade.


A bit of an update (a good one). So in replacing the ecu, I decided it was time the bike had an oil and brake fluid change as they had not been changed since 2008 😳😳😳

Anyway, the bikes only done 200 miles in 13 years with the previous owner, so have done a 170 mile blast from darkest Shropshire to darkest Cambridgeshire this afternoon..... And what a bike! My god it goes like a train and then some. And a smile so large on my face the internal sun visor stopped people being blinded as I went past.

So so different in nature to my ST2 and 748.

A very happy Keith 😊