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Advice needed on sick Stone please!

Gwilliam

Gwilliam

Tuned and Synch'ed
GT Contributor
Joined
Jan 28, 2009
Messages
61
Location
Guildford, England
Hi,
I have a 2001 California Stone which several members have been very helpfully providing assistance with lately.
For the last year or so it has been popping and banging in the exhaust on light throttle in traffic as it goes from drive to over run and back to drive.
It also occasionally spits back through the air filter as part of it's performance! This all makes it unpleasant to drive around town. On open road with larger throttle openings it goes fine.

I thought that I would try to finally fix this as part of a large service. I have tried balancing the throttle bodies on previous occasions but it has never fixed the problem. So after changing all the oils, filters, plugs and adjusting valves I decided to attempt to set up the throttle position sensor.
I have read up on this procedure and followed the step by step instructions achieving the closed throttle 150mv, followed by 520mv after adjusting the right hand idle screw. I then adjusted the left hand screw until it just moved the 520mv and then backed it off a whisker.
I turned the idle air screws right in and back out half a turn and started the bike. Despite my having ensured that the fast idle adjusters were not in play it would not run below 1500 rpm and I could get nowhere near balancing the throttle bodies.
I took it apart again and rechecked my mv settings which were acceptable. I did tweak the idle screws just to the correct spec as I had twiddled them the first time in an attempt to improve things.
I ran the bike again.
The right hand cylinder was doing very little, as before, punctuated with spitting back through the inlet and blowing the push fit vacuum gauge hose off the manifold. This shows up on the balancing sticks with the left cylinder having a much higher vacuum than the right. Adjusting the idle bypass screws has no significant effect.
Where do I go from here? All and any suggestions welcome!
Thank you.
 
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When I zero a TPS, I don't touch the right side throttle stop, but remove the e-clip on the left side throttle rod and unhook the throttle rod that moves the butterfly valve. That way noting can interfere with getting the butterfly completely closed. What condition are the rubber pieces that connect the throttle bodies to the cylinder manifold? It sounds like you have one heck of a vacuum leak. Also have you done a compression test?
 
I've replaced 3 TPS units in 180000 miles. If you haven't do so now. research it here there are reasonably priced ones out there. did you clean the cam position sensor? have you replaced all of the relays with new 5 prong ones and sprayed the holders with deoxit. same with the fuses. replace and clean.
Go back and do what john said and spray around the intake boots while running with carb cleaner to see if it dies or acts up meaning an intake book leak. when did it run right last. you gave us little info.
 
And John rides to the rescue once again, like the 7th Cavalry, with bugles blaring! :)
I had never done the TPS before so stuck to the instructions.
I have been pondering this problem for the past couple of days which is what led me to try the TPS. I had thought either that or an air leak because an air leak would be most noticeable at smaller throttle openings. However, I am struggling with it being an air leak because the path between the throttle body and cylinder head is so short and simple that it is hard to believe that a leak of such magnitude wouldn't be obvious. Nevertheless, I shall try spraying copious quantities of carb cleaner around the area with the engine running and note any changes.
One other simple test that I had overlooked is to try swapping the plug caps left to right - I'll kick myself if that turns out to be the problem.
I haven't done a compression test, but I will, although it runs so strong when accelerating hard that I think that the engine is sound.

In answer to Vagrant, who has joined the discussion while I am typing - the bike has done 32000 miles. The TPS has never been touched until today - the yellow factory gloop still covered the screws. I have a Harley dealer local to me and I vaguely remember that they use a similar unit - I will check it out.
I will also try the relays and fuses.
The bike has had an issue with rough running on light throttle - popping in the exhaust and some spitting back through the air filter over the last year or so but has done very little (sub 1000) miles in that time.

Thank you both for your Input.
 
Hi guys,

Today's update on progress or lack thereof!

I started off by switching the plug caps - it made no difference.
With the engine running, I sprayed a lot of carburetor cleaner all around the right hand cylinder head to intake manifold joint, then along the rubber "boot" joining the manifold to the throttle body. It made no difference to the running.
I repeated the process on the left hand cylinder. The rubber boot has looked quite perished for a while but I have been assured that the rubber is very thick and that I shouldn't worry. However, there was a definite improvement in the running and the carb cleaner disappeared. As I had bought a new boot a while back when I noticed the correct one come up on eBay I fitted it.
Unfortunately, it didn't fix the problem.
I removed the plugs and performed a compression check - both cylinders produced an even 135 psi.

Following Vagrant's suggestion I removed and cleaned the cam position sensor, assuming that it is the component adjacent to the oil pressure switch! I seem to remember reading that these are shimmed to suit each engine. For what it's worth, mine has an 1.03 mm aluminium shim beneath it. After starting it up I thought for a couple of seconds that there was an improvement but the problem returned.
I removed all the fuses and relays and sprayed switch cleaner into the holders. I fitted a new set of fuses of the correct values as per the side cover and handbook. The originals had a couple of higher ampage. I cleaned up and refitted all the relays ensuring that they went back in different sockets until I can get some new ones.
Upon starting, the regular spitting back through the inlet continued.

My neighbour has an EV and a wrecked EV as a parts donor. He gave me the ECU to try as I had been suggesting that I would like to borrow an injector. He thought that it may be worth trying the ECU first in case it wasn't communicating with the injector properly.
It was an IAW15M.C1 whereas mine is a IAW15M.C3 but I fitted it anyway. The engine fired up but was running at around 2000 - 2500rpm. Initially I thought that it was because the right cylinder was contributing more effort but after some twiddling to get the engine speed down the spitting back resumed.
I refitted the correct ECU.

As far as I am aware spitting back in the inlet is usually caused by a weak mixture taking longer to burn or retarded ignition. Either of those conditions result in the fresh mixture being detonated as it enters the cylinder causing a pressure wave to run back up the inlet tract.

Do injectors fail very often?
Is it possible to remove one and see if it is firing a spray pattern rather than a dribble?

Finally, I contacted a local Harley dealer about a replacement TPS . The part number that John kindly supplied is for early bikes and is no longer available.
I may try borrowing one from the donor bike to try!

Any further help or suggestions much appreciated!
 
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Compression looks a bit low, but at least they are even. Did you have the throttle bodies wide open when you did the test? Yes the injectors can be removed, but with their location they are not easy to get to. Requires removing the airbox to gain access as they are located on the inboard side of the throttle bodies.
 
Hi John,

Yes I had the throttles wide open during the compression tests.
It has been suggested to me that it may be worth running a can of injector cleaner through it, although I feel that more drastic measures are going to be required.
I am sure that I have yet to identify the cause of the problem.
I have booked it in with a Guzzi mechanic of many years
standing who is generally well regarded by many owners. If I haven't managed to get it sorted by then hopefully a fresh approach may make the difference.

Do you know of another way of setting up the TPS as he said that he doesn't do it using a voltmeter? That worried me a little but I'm prepared to try anything at the moment.

I intend to try riding it tomorrow just to see if it still behaves the same on the road. The tickover is if anything worse than before, with constant spitting back through the air filter but it will be interesting to see if the exhaust popping has changed on the road.

I will report back later!
 
The initial zero of 150 MV must be done with a meter. I do use software to read the TPS when opening to 3.6 degrees for the 15M, or 2.1 degrees for a P8 bike. As to injector cleaner, you may get good results with a product called BG44 which I hope is available in the UK. Using the BG44 sure beats trying to get to the injectors. Use the whole bottle with a full tank of fuel. See the thread on Alaris and the PDF on page 2 of this thread for the California Vintage. The TPS setting is the same for your bike. https://www.guzzitech.com/forums/threads/new-alaris-centurion-vdsts-info-instructions.1676/
 
I believe that I may have fixed it!
During the process of swapping HT leads around this morning I accidently ran it on only the left hand cylinder for a minute. Apart from the obvious lumpiness, there was no evidence of all of the spitting back through the air filter. That confirmed that the problem definitely originates with the right hand cylinder.
As I had pretty much eliminated all of the ignition components, I returned to my idea of a failing injector.
At low engine speeds and small throttle openings slightly erratic performance is more noticeable than when it is firing pretty much continuously into a large volume of fast moving air.
Luckily the injectors fitted to my neighbour's scrap EV are the same as my Stone.
They are actually pretty easy to change if you remove the four throttle body to retaining brackets screws, the circlip on the throttle linkage and the rubber boot clamps. You can then disconnect the fuel pipe and electrical plug and pull the throttle body out without removing the fuel tank or air filter box. The injector can then be removed from the throttle body by removing the two allen screws and pulling it free from its two O ring seals.
Having then reversed the process to install the donated injector, I fired up the engine which ran happily on both cylinders.
I have yet to connect my voltmeter to reset the idle screws to attain the listed 520mv and synchronise the throttle bodies with my carb sticks but I am confident that tomorrow will see the conclusion of this tale.

I am glad that I stuck with it and didn't just start buying components without proving that they had failed first.
I was lucky in this by having a suitable donor bike available.
When I stated checking the listed prices of new Moto Guzzi parts I was horrified to discover that a Throttle Position Sensor is €411.29 and Injectors are €951.62 each!
The rubber boots for the throttle bodies are around £50.00 each and even the moulded breather hose from the top frame tube to the crankcase breather valve is in excess of £60.00.
I had never realised what a valuable bike I have been riding for the past several years. It is pity that value is not reflected in the price of used bikes!

Anyway I would like to thank all who have helped with advice and suggestions, allowing me to solve the problem.
 
Take that injector you removed to a diesel shop. They may know a source that can re-condition it. I hope that injector is the solution. Good job hanging with it and doing proper troubleshooting. Also I haven't tried your method of getting to the injector. I'll keep it in mind. I checked the US price for the injector. Crazy as Guzzi doesn't list just the injector but the complete assembly. Too bad it isn't the same injector the 750 Breva uses, they are less than $80.00 USD, and the 1100 Breva is $163.00 USD.
 
Hi John,

I had the reconditioning conversation with my neighbour, the owner of the donor bike. He thought that at 32000 miles the injector must be repairable. He has an ultrasonic cleaner that he is interested in trying on it.
Whilst it only takes about 30 minutes to change the injector, I don't need the practice of keep swapping them back and forth to see if he has fixed it! I don't even know whether it is an electrical problem intermittently causing it not to switch on or a valve sticking producing a poor spray pattern.

I will do a bit of research on repair shops today.
Forty-five years ago, in my apprenticeship days, I remember setting up diesel injector pressures and checking spray patterns etc. They were mechanical in those days and could be bolted into a hydraulic test rig on the bench so that you could pump up the fuel pressure until it fired. You could adjust the injector to fire at the appropriate pressure and check the spray pattern at the same time.

The parts book exploded diagram shows the injector in several pieces but as you say, it is only sold as an assembly of all those parts - for a ludicrous price!
What is so different about the Breva injectors that make them so much cheaper?!!! Maybe they don't come as a series of components that may be dismantled and overhauled? I guess that I may know more after some research on reconditioning.
I would have thought that Moto Guzzi dealers must have encountered this problem and possibly found a solution.

I'll let you know if I find anything interesting.

Regards,

Clive
 
Well that was a bad day!

It was 33°C here today, far too hot to be fooling around with broken bikes without any shade!

I made some calls and found a company to overhaul the Weber injector so mailed it to them.
When I got back from the post office I went out to set the throttle bodies to the 520mv idle setting and synch them before road testing the bike. All went well until I started it for the synching - and we're back to all of the spitting and popping, blowing the R/H carb stick pipe off the manifold etc.
I could have cried!!!!
The vacuum is still so low/non existent on the R/H cylinder compared to the left, so in desperation I removed and inspected the R/H inlet manifold. I refitted it with a smear of silicone on the undamaged gasket face and swapped the rubber boot from the donor bike which of course made no difference at all!

I took it for a ride and it is not good, it misfires, pops and bangs from the exhaust on overrun and light throttle. When you hit a dual carriageway and can accelerate hard it is fine.

I'm getting close to leaving it to a new player with fresh ideas and experience. Tomorrow I may try swapping the L\H throttle body with the TPS and the cam position sensor, just for something else to try. However I can't understand why they should cause the symptoms that I am experiencing.

Help!!!
 
Doubt it is the cam position sensor. Without being able to put hands on I don't think there is much more we can suggest. One last question, How do the plugs read? championautoparts.com/Parts-Matter/automotive-repair-and-maintenance/how-to-read-spark-plugs.html
 
I do appreciate that I am setting you an impossible task.
I can't figure it out am I have it in front of me.
The plugs are new and are showing a normal greyish colour.
I will probably try the L/H throttle body first complete with its TPS. I no longer have much confidence in most of these operations but it is something that I haven't so far changed. The original does give the correct millevolt readings both when set and returns to it upon closing the throttle so what more can I ask of it?

I will let you know if I ever find out what is going on with it!
 
If the TPS were the faulty component, both sides would be effected. Something just isn't working properly on the right side. This is such a long thread, I can't recall if you have tried swapping coils side to side to see if the trouble moves. An engine is basically just an air pump. If the cylinder is healthy, you should have good vacuum unless air is getting to the intake track somehow.
 
That is what I keep coming back to - I have changed the leads and the caps and the plugs but not the coils.
Stupid really but the Guzzi mechanic said that he'd only ever known two fail and one of those was one that he blew up himself!
It seems strange that there us no misfire under large throttle opening and high revs but everything seems strange at the moment.
It is a pretty simple job to do the coils so I'll go and attack the donor bike again!
Thanks John!
 
Well I changed the R/H coil and started it up. It seemed better but has caught me out before when starting on a fast idle from cold.
I tried adjusting the air bleed screws in the base of the throttle bodies to synch the two. It had little effect so for a change I tried the screw for synching the throttles higher up the rev band. By this time it had warmed up a little and started spitting back in both cylinders and blowing off the vacuum gauge tubes. It had never done that before.
I wondered if maybe there was a problem with the L/H coil as well, so swapped that too.
It didn't help.
I've messed about with several misguided theories throughout the day and ended up pretty much where I started. I have now got a different pair of coils installed though I may yet change them back.
The one constant is that all of the popping and banging stops if I remove the plug lead from the R/H cylinder. The engine runs happily on the L/H cylinder, reving, running at light throttle and idling with no misbehaviour. As soon as I reconnect it the problem is back. It appears to fire when it feels like it irrespective of where the valves are at the time, causing it to detonate in the inlet valve and/or the exhaust. It ends up working against the L/H cylinder rather than with it.
Presumably all such things are controlled by the ECU?
 
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