Decat headers with Hilltop

[newman7096]

I had hilltop done a while ago and was really impressed but my bike had got decatted original headers. I'm wondering if proper decatted headers would sort out some of the remaining low down lurching below 3000rpm.

Any ideas?

 

[Kenny Rodkiss]

I would find out why it's misbehaving below 3000 first!

 

[newman7096]

Hilltop got rid of a lot of it when it was done so it's obviously a fueling issue. Just a bit left that cause issues at slow speed i.e. filtering. I've had quite a few GS's and this one appears more lumpy than normal. Maybe secondary coils. I don't like to guess I'd rather throw money in the right direction.

 

[Bendy toy]

the ECU will adapt between decat and standard headers so I'd not expect the misfire to change. Check the coils and fuel pump system.

If the pump pressure is low fuel wont atomise properly sometimes causing lumpy running at lower revs.

If a coil is misfiring that side will run rich. O2 sensor sees unburnt oxygen (it can't see unburnt fuel), ECU adds more fuel to compensate for what it thinks is excess oxygen.

 

[newman7096]

I think secondary coils are next on the list followed by headers if I can find and second hand

 

[Greenman14]

The Hilltop map should self-adjust to the small difference between your butchered OEM headed and the real thing. I had my TC Hilltopped with the Standard headers then fitted a set of decat headers later; the bike ran just fine before and after the header change. I think you have another different problem.

 

[newman7096]

Found the problem! Took the bike for a run today did about 70 miles. The engine was nice and hot and whenever it hit the magic 2000 to 3000rpm it would start its lurching, hunting. Decided to do the coil check procedure when I got home.

Disconnected the secondary coils and took it for a spin whilst it was still warm and could tell little or no difference, still lurching etc. Stopped at the side of the road and reconnected everything and then disconnected the primary's. Started the bike, or tried to.....cough, splutter, bang pop as it turned over followed by backfire. Wouldn't event start on the secondary's.

Think I've had this problem ever since I've had the bike and blamed it on the fueling. I'm quite excited now by getting some new coils.

 

[younger06]

Are the coils an expensive job?

Sent from a OnePlusX.

 

[newman7096]

Secondary's are about £100 a side and primary's are £80 to£90 per side!

 

[Bendy toy]

It sounds like primary coils. The old black painted type will smell burnt when failing though thy still spark (badly). Eventually they give up altogether. When one fails the other side will go soon after.

See if you can borrow a pair of primary coils.

 

[newman7096]

It sounds like primary coils. The old black painted type will smell burnt when failing though thy still spark (badly). Eventually they give up altogether. When one fails the other side will go soon after.

See if you can borrow a pair of primary coils.

Bike runs fine on primary's, won't run at all on secondary's.


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[Bendy toy]

I could throw my secondaries away and not notice any difference but the 2ndry plugs are both a good colour so they must be sparking.

If you have confirmed the coils are ok, your problem might be weak fuel pressure. The fuel wont atomise properly at low throttle/low revs making engine run rough. Generally not an issue at higher power levels.

Weak coils will often run fine when you swap them left/right. The only sure test is try the bike with two known good coils.

 

[newman7096]

It runs fine on primary's. Won't start or run on secondary's and it should. That tells me the secondary's are at fault. I will in time replace the primary's but don't believe they're causing this issue.

 

[Bendy toy]

You are probably right about your primaries but speaking from experience mine did the same. One primary finally packed up totally so off I went to North Oxford BMW for a new coil. The other coil failed totally while I was riding home. Not a low cost trip TBH. But its run fine ever since and still wont run on secondaries only.

If your primary coils smell burnt, they have to be in the frame. If not, (as you say) move on to the next test. Weak fuel flow will affect how the engine runs.

 

[newman7096]

As my bike is a 2009 with 36000 miles and still on the original coils I decided to bite the bullet and buy four new coils. Bike now nice and smooth again. Lurching gone, ride happily at lower rpm ��

 

[Bendy toy]

As my bike is a 2009 with 36000 miles and still on the original coils I decided to bite the bullet and buy four new coils. Bike now nice and smooth again. Lurching gone, ride happily at lower rpm ��

What happens when you disconnect the secondary coils (unplug the cable connectors)?

 

[newman7096]

What happens when you disconnect the secondary coils (unplug the cable connectors)?

Disconnect secondary's and bike runs fine. Disconnect the primary's and bike starts and runs fine. Had to remove the sealing rubbers from the old primary coils and swapped them over to the new ones. Hopefully all sorted for another 30000 miles at least


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[Bendy toy]

Sounds like the coils are Aok