12425 - Established June, 2013 - all GRiSO, all the time...
 
HomeFAQRegisterLog in
Share | 
 

 High speed, low throttle stumble/power dip

View previous topic View next topic Go down 
Go to page : Previous  1, 2, 3, 4, 5
AuthorMessage
MotoMT
Carlotto
Carlotto
avatar

Posts : 37
Join date : 2016-08-02
Age : 38

PostSubject: Re: High speed, low throttle stumble/power dip   Fri Apr 07, 2017 11:45 am

Update: So I've pulled the gear off and wiggled everything around to line up properly at tdc, per Pete's instructions. Interesting finding, though: The bolt was stressed significantly, like almost to the point of breaking! I'll post a photo later, cause it's nuts how distorted it is!

It came out easy enough, but why the hell would it be over torqued so badly? Bad day at the factory? Or was someone in there previously for other work? Meh, who freaking knows?

Anyway, the bolt is on backorder a few weeks. It's a flange bolt M8 1.0 threads, grade 10.9, part 1A000425. Any issue with using a regular hex bolt and washer with the same specs? Other than not dropping the washer in no man's land, are there other worries with not using the flange bolt (that'll be like $12 shipped)?
Back to top Go down
Pete Roper
GRiSO
GRiSO
avatar

Posts : 4424
Join date : 2013-05-29
Age : 60

PostSubject: Re: High speed, low throttle stumble/power dip   Fri Apr 07, 2017 1:54 pm

Not that I can think of but make sure you use a reasonably high tensile bolt and a dab of Loctite 243. Also make sure the locator peg is covered by the flinger disc not aligned with one of the holes!

Pete
Back to top Go down
MotoMT
Carlotto
Carlotto
avatar

Posts : 37
Join date : 2016-08-02
Age : 38

PostSubject: Re: High speed, low throttle stumble/power dip   Fri Apr 07, 2017 9:07 pm

This is the bolt that came out of the right side. It holds the upper sprocket on the cam, or service shaft, or whatever the hell MG calls it.

It's stressed, looks about ready to snap about 1/3 down from the flange. And I'm assuming it's not supposed to be? This is the way it came out! I couldn't believe it when I saw it. The bolt is small: M8x1.0 and 25 mm or so. The torque is something like 22 ft-lbs, if I remember correctly. It just doesn't need much muscle to tighten, so WTF?

As far as I know, the bike never had any work done previously. A 2015 with ~3000 miles when I bought it. At this point, I don't care as long as I get it running like it should. Still interesting to see mysteries like this, though. scratch

[You must be registered and logged in to see this link.]
Back to top Go down
MotoMT
Carlotto
Carlotto
avatar

Posts : 37
Join date : 2016-08-02
Age : 38

PostSubject: Re: High speed, low throttle stumble/power dip   Sun Apr 09, 2017 12:46 pm

SUCCESS!

Got everything put back together last night. Just returned from a test ride. Power all the way to redline! 

Idle running and power under 5,000 rpm are better, too. Although without context previously, it seemed OK. It was anemic even though I thought it was running OK up until the power loss.

This was major surgery for me. But for fellow mechanically disinclined folks who don't have access to an MG shop, it's doable. Just make sure to go slow and learn from my mistakes (there were plenty). I tend to go down rabbit holes needlessly and had a few clueless wild goose chases (as mentioned in previous posts of this thread).

Here are things I learned (thanks for the knowledge around here):

1) The exhaust header gaskets get squished down once installed. It may appear there are no gaskets, but look closely, they are there. Surprised

2) The TPS sensor reading in Guzzi Diag can bounce around a bit when the bike is idling. This is normal, don't freak out.  Razz

3) Empty the gas tank before trying to remove it. Also, unplug the fuel pump connector and cycle the starter to release some pressure before unplugging the "quick" connector. Otherwise, you'll get angry. OR just leave fuel hoses connected and remove them with the tank. It's easy to disconnect at injectors and lift tank from there. Just don't kink the fuel lines.

4) If you use a ratchet to turn the crank, for setting valve clearance, etc. DO NOT be a dumbass and leave your ratchet on the nut when you start the engine. Don't ask me how I know this ...

5) Loctite 243 is oil resistant and is different than 242, hahaha!
Back to top Go down
Pete Roper
GRiSO
GRiSO
avatar

Posts : 4424
Join date : 2013-05-29
Age : 60

PostSubject: Re: High speed, low throttle stumble/power dip   Sun Apr 09, 2017 3:01 pm

Looking at that bolt I'd say that it must of been apart at some point as the factory probably use pre-set torque ratchets for assembly and I've never seen a bolt that stretched.

You got the bike with very low miles. I'm betting that it had that head off for some reason, (Casting porosity maybe?) and was reassembled by one of our hairless ape bretheren, hence the stretched bolt and mis-timed cam.

Pete
Back to top Go down
 
High speed, low throttle stumble/power dip
View previous topic View next topic Back to top 
Page 5 of 5Go to page : Previous  1, 2, 3, 4, 5

Permissions in this forum:You cannot reply to topics in this forum
GRiSO ghetto :: The Ghetto :: GRiSOLOGY-
Jump to: