weird technical problem. Or is it ?

[jihem]

hi all,

 

My bike has developped a weird behavior.

 

Last week, I took her to a dyno specialist, and prior to that all levels and check were made at a good Guzzi shop, meaning all valves, TPS, etc...were fine. Bike was running good I must say, if only it had that weird behavior at higher rpms which the dyno would tentatively take care of (the bike has a RS Scola cam, and a PC III, and it seemed like the Ghezzi frame wasn't allowing the newly testosteronized engine to breathe enough).

 

The Dyno guy took the bike and enhanced all parameters as well as his experience and the numbers told him to.

 

(I'm reasonably happy with the numbers as it's now 83 CV rear wheel, up from the stock engine at 60 CV (i have the official homologation documents). 30 % more rear wheel power isn't bad altho i really thought the RS cam would move the engine further up the CV ladder. The Dyno guy says he can tweak about 3 CV more without too much hassle. I wonder why he didn't then )

 

I went to get the bike, tried him for a few miles and, yes, the ugly dip at high rpms was gone, thanx to a good dyno ear and BMC pods. So, I paid and I left the dyno shop.

 

A few miles later, the bike begins to pop, I thought I was about to run dry so I fill the tank. No, the bike would still pop like crazy, run on one cylinder (it's the left one that pops), then the idle would go up to 3000 rpms, then cut, go back to 3000, etc...But above 4000 rpms, the engine works fine. I succeeded going back to brussels, on the motorway (above 4000 the bike runs good).

 

The morning after, I start it, hoping the phenomena was only due to the engine at warm temperatures (altho the PCIII doesn't care about heat apparently). It was exactly the same. So , i changed sparks, hoping that would solve it, altho both sparks were only a few weeks old. They were black, but new ones didn't cure the engine either.

 

I have taken the bike to my regular shop, not a Guzzi specialist, but the mechanic there knows my bike very well and he's going to try to locate the problem as the Dyno guy would like him (they know and respect each other) to look out for things like a bad injector, or a coil or... before I eventually go back to the dyno. My reason for not going back to the Dyno shop directly is that he has no knowledge of guzzis, and no real access to parts so having the bike opened up there could be messy and long...

 

What do you think ?

[Tom M]

Sounds like an air leak to me but I would think that the left plug would look lean not rich

 

Have you checked your intake boot for cracks?

[jihem]

Sounds like an air leak to me but I would think that the left plug would look lean not rich.

Have you checked your intake boot for cracks?

 

 

yes, they are fine...

 

mmhh..

[dlaing]

Jaap had a similar experience after a dyno session.

I wonder if the dyno operators are trying to get more power out of the bike by making it run lean and hot at mid throttles, also giving you better fuel efficiency.

From what I understand, a hotter engine develops more power, so when you transition from too lean to rich enough, you get more power, atleast on the dyno printout.

But the lean conditions at some map positions could be causing the popping, and other positions on the map are rich, so the plugs don't indicate the lean problem.

Also the fact that the popping is on the left, it could be the dyno guy sniffed the right side only.

Perhaps the dyno operator can dump your old map back into the ECU in five minutes.

But I think the idea that it may be an air leak, cracked boots or leaky exhaust gasket, are more likely the problem.

[jihem]

Perhaps the dyno operator can dump your old map back into the ECU in five minutes.

 

well, it could indeed be an interesting thing to do if the shop doesn't find anything. But the bike has changed a lot since the last map: it has now BMC pods instead of the frame as airbox...This said, if the poppings stops, or move along the scale, that would be a sign...

 

But I think the idea that it may be an air leak, cracked boots or leaky exhaust gasket, are more likely the problem.

 

i surely hope it's something that "simple".

[Guest Nigelstephens]

If it has only happend since the dyno my guess is that it is the map settings or some stress caused by the dyno session.

 

I good thing to try is to remove the tank and seat and check all the connector plugs including the ecu. Check for corrosion and signs of poor connections. There are many connectors in the ECU and sensor system so take your time.

 

I have heard that the rpm(timing) sensor can cause strange affects. Its near the top of the front cam chain chest at the front. Its worth checking that this connector to the loom is making a good contact. The pickup itself can cause problems. Please would someone correct me if im wrong.

 

It does sound like a timing problem at low revs. I have had a poping when I have moved the TPS the wrong way. So if this is the case its the timing pickup (described) or the ECU map or ECU/PCIII.

[Alex-Corsa]

 

But I think the idea that it may be an air leak, cracked boots or leaky exhaust gasket, are more likely the problem.

 

Also, except all these mentioned , faulty intake valves-guides can cause some "strange" poping as well(especially at idle), check out , is there any "side-play" at the valves?....been there and done that

[jihem]

But I think the idea that it may be an air leak, cracked boots or leaky exhaust gasket, are more likely the problem.

 

you had it right: an air leak on the left hand BMC pod. You could barely see it but it had a lot of negative effect. It's fixed now.

 

thanx all !

[Admin Jaap]

As Dlaing said, I'm experiencing the same problems. Today I went to Assen to see my nephew race his R1. Under 4000 rpm the bike ran like crap!

 

Jihem, where did you find the air leak? Between the throttle body and cilinder or between the throttle body and filter?

 

BTW, fuel economy is definetly better after the dyno run. Normally, the fuel light came at about 210 km. Now it wasn't even burning at 230 km.! (At 230 kms I had to stop because my brother's Sir Drinkalot (Triumph SpeedTriple) needed fuel.)

[Admin Jaap]

I found the culprit...

 

The 4 cm. (!) crack was below the "slangklem" (Couldn't find the english word. ) so I didn't spot it right away.

[g.forrest]

I found the culprit...

 

The 4 cm. (!) crack was below the "slangklem" (Couldn't find the english word. ) so I didn't spot it right away.

 

yes..''slangklem'' can't find the answer..but yes it's rooted.

[jihem]

Jihem, where did you find the air leak? Between the throttle body and cilinder or between the throttle body and filter?

 

it was between the throttle body and the filter. But it's fine now

[Admin Jaap]

Thanks.

 

I ordered a few of these rubber hoses at TLM (part # 01114300 ) to put on my garage shelf.

Next weekend I'll ride without problems (knock on wood) to the Italo Day in Amsterdam.

[luhbo]

Thanks.

 

I ordered a few of these rubber hoses at TLM (part # 01114300 ) to put on my garage shelf.

Next weekend I'll ride without problems (knock on wood) to the Italo Day in Amsterdam.

 

Don't overtighten them. This is what kills them, not so much the ageing. If you see the rubber becoming deformed it's definitely to much.

 

Hubert

 

BTW, a comparison between your now optimised ecu and the Titanium race ecu would be most interesting. Any plans in this direction?

[Martin Barrett]

I found the culprit...

 

The 4 cm. (!) crack was below the "slangklem" (Couldn't find the english word. ) so I didn't spot it right away.

 

Jaap, was that the one from the left or right. It was your left that popped off mid ride at the German V11 Treffen.

I wonder how much the splitting was due to overtightening ( he might have small ladies hands but has a good grip )?

 

 

My left one popped of a couple of years ago

and at the end of last summer kept coming adrift and splitting. I'd wrapped with insulating tape whilst waiting for the replacement. I think my right is going the same way, but I have the spare ready.

I think I'd probably ended up over tightening.