Triumph Rat Motorcycle Forums banner
  • Hey everyone! Enter your ride HERE to be a part of this month's Bike of the Month Challenge!

1 - 9 of 9 Posts

·
Registered
Joined
·
22 Posts
Discussion Starter · #1 ·
My Speed 4 has developed a weird engine noise and thought I'd see if anyone has any ideas?

It's a rattly clicking noise that's pretty loud and only starts at about 6000rpm and then grows in frequency with the revs until I can't hear it over the wind noise. The strange thing is that it only happens on a positive throttle, it stops as soon as you stop accerelating and go onto a neutral or negative throttle.

Also, the noise only happens when riding and can't be replicated just revving the bike while stationary. However if I rev it at a standstill I think I might hear just one knock as the revs rise but it could just be in my head.

I think that's about it, any ideas gratefully received.
 

·
Premium Member
Joined
·
2,522 Posts
Have you checked the chain lately?
 

·
Registered
Joined
·
22 Posts
Discussion Starter · #3 ·
The chain is spot on. I recently gave it a good clean and lube, I even had the front sprocket off and cleaned behind there!
 

·
Premium Member
Joined
·
2,522 Posts
How about the chain's condition? Are the sprockets worn, are any rubber o-rings missing from the chain? I'm not sure if a warn out cush drive in the rear wheel would cause the noise you describe, but it would make since that it only happens under load.
 

·
Registered
Joined
·
22 Posts
Discussion Starter · #5 ·
The chain and sprockets are only a few thousand miles old and pretty much as good as new. The cush drive is fine as well.

The noise happens under load but only starts at 6000rpm every time, no matter how hard or softly I accelerate.
 

·
Registered
Joined
·
22 Posts
Discussion Starter · #6 ·
Just got back from the garage, they're a Triumph specialist so know what they're talking about.

Turns out it's the crank!

The mechanic took it for a spin and within 100 yards turned around cos he knew exactly what it was.

I'm absolutely gutted! It wasn't the latest or best bike but it was spot on for me, guy at the garage said it was the nicest example he'd seen.

Now I need to decide between getting a recon engine or just chuck it on fleabay and start again?
 

·
Premium Member
Joined
·
2,522 Posts
Not to insult the mechanic, but I would go to another reputable shop for a second opinion before doing anything. A rod knock or spun main bearing noise can occur only when the engine is under load, and the knock is usually worse under load and when the engine is hot. However, you can usually hear the knock when the engine is not under load too, which you say you cannot.

Although the mechanic is a Triumph specialist, these engines make a ton more noise than most, and he/she might not have a lot of experience with Triumph inline four 600/650cc engines. I'd bet that if you took a brand new Speed Four to 10 mechanics, most would tell you there is something very wrong with the engine just because of the noises it makes.

If it does turn out to be a bad bearing or journal issue, check to see what the mechanic would charge to put new rod and main bearings in (it will be just an estimate until he/she inspects the crank and line bore). If that's too expensive, used engines are around for under $700 shipped (in the USA). You'll want to be very careful when getting a used one to make sure it has the miles on it that are advertised and that it is in good condition.
 

·
Registered
Joined
·
22 Posts
Discussion Starter · #8 ·
It's definitely the crank, the mechanic said that the noise is unmistakable and bloody loud, when he rode off on it, it was even louder than I thought. The cost of stripping, fixing and refitting the engine was obscene (2 grand plus) so it's going of to Sandy at Triumph-ant to have the engine refurbed. £1000 all in, I'll be skint but the bike will be good as new.
 
1 - 9 of 9 Posts
Top