Author Topic: 850 T3 Cali rough between 2000-3500  (Read 443 times)

Offline Adv_hoon

  • New Egg
  • *
  • Posts: 24
850 T3 Cali rough between 2000-3500
« on: May 24, 2022, 05:26:25 AM »
I recently bought a 1977 850 T3 California which runs really rough between around 2000-3500 rpm. If I crank open the throttle completely in that rpm range then it bogs down until i turn the throttle back and it slowly picks up. Once it is past 3500-4000 it pulls fine with wide open throttle although I think it may be slightly rich there as it pops on overrun. But that is the least of the worries.

I had a theory that it might have something to do with it being bored or fitted with 950 barrels, as it came with some documents that could point in that direction. And hence the carburators perhaps not being properly jetted. I abandoned this theory somewhat for being the full cause of the issue as from what I could read it might not need the biggest of change in jetting, even if it was 950. I pulled the slides out and found V9 needles in the lowest setting (meaning richest - as far as I know) so seems like something else is wrong. The slides did appear very worn though, so perhaps that is part of the issue?

Recently it started dropping one cylinder and had a hard time idling. I have synchronized the carbs and with some more adjustment of the idle mixture screws (only like a quarter turn) I could get it to idle properly although it seems like it very, very slowly dropped the idle. After this I went for a test-ride and when I accelerated then one cylinder would drop and then come back. This let me to believe that perhaps it has to do with ignition and low voltage instead? Perhaps the spark is weak and when the mixture is absolutely perfect at idle, then both cylinders can run, otherwise not. I have never before experienced that a quarter turn on the idle mixture screw could have the cylinder drop off?

Another reason for suspecting low voltage is that the PO just replaced the battery and starter before I bought it. The charging light also comes on at low rpm when you start it and actually only turns of once you go above 2500-300 rpm or something like that.

It will be a couple of days before I have time to work on the bike again. But how much voltage should I expect at the battery at around 1000, 2000, 3000 etc? As far as I have read it should be around 14 volt from 3500 and above?

One little side note which may point to the fact that I have more than one issue, is that it has really bad gas mileage. Just driving around country lanes I have gotten like 13 km/l (around 30mpg) and from what I have read here on the forum and elsewhere that is very low. So perhaps it is a combination of ignition and carbs.

So any thoughts on what might cause it to run very badly in roughly the 2000-3500 range and not allow full throttle is highly appreciated. Can it really be that WOT "blows out" the spark because of low voltage? My initial thoughts would be some acceleration circuit not working, but with all the other issues I at least think spark/ignition has something to do with it. As I said it will be a few days before I can work on it again so just collecting things to try and test for when I will work on it again. And sorry for the wall of text, just wanted to give some context and share my thoughts to make it easier to form an opinion.


Online chuck peterson

  • Gaggle Hero
  • *****
  • *
  • Posts: 4803
  • Location: New Haven CT
Re: 850 T3 Cali rough between 2000-3500
« Reply #1 on: May 24, 2022, 06:32:32 AM »
As TOMB told me over

And over..

And over…

And over again…


Change one thing at a time…I think I’d try lowering (less fuel) the needle a notch or two, and ride it to test the effect

But the rest is Gap? Timing? Tappets? Tune up?

Good luck! Let us know
"I'd like to thank all my friends who have kept my Guzzi's going, but mostly...TOMB."
150k on Verts
750 Nevada
400f
R5 Yammie
BV250
4x 1976 Moto Demm Smily,, now 5, oops now 6, oops now 7
1980 SP1000 in little bits and pieces

Online moto

  • Gaggle Mentor
  • ****
  • *
  • *
  • *
  • *
  • Posts: 574
  • Potrebbe andare peggio, potrebbe piovere!
  • Location: Madison, WI
Re: 850 T3 Cali rough between 2000-3500
« Reply #2 on: May 24, 2022, 06:50:00 AM »
Changing things one at a time is the right way to go of course.

But before that, does the motor have good compression? Do a test.

Check the mixture at 2500 rpm by pulling the enrichener lever(s) on the carbs while riding down the road. If the motor runs stronger, the mixture was too weak. If it bogs or quits, that is a sign it was either okay or too rich.

Are the openings in the mufflers covered in carbon?

What do the spark plugs look like when you do a plug chop?

Sorry to have hit the post button too soon, earlier.
« Last Edit: May 24, 2022, 07:02:51 AM by moto »
850 T-3
Griso 1100 corretto
Italjet Buccaneer 250 (ex-SSR)
credit for 2500+ postings lost in the database meltdown of Feb 9, 2020

Offline Adv_hoon

  • New Egg
  • *
  • Posts: 24
Re: 850 T3 Cali rough between 2000-3500
« Reply #3 on: May 24, 2022, 06:53:18 AM »
As TOMB told me over

And over..

And over…

And over again…


Change one thing at a time…I think I’d try lowering (less fuel) the needle a notch or two, and ride it to test the effect

But the rest is Gap? Timing? Tappets? Tune up?

Good luck! Let us know

Yes. Could not agree more. That is also why I think I will start by checking the charging as that is what the "dropping" of one cylinder points to in my head.

As with regards to the needle I actually tried all three settings and raising it made it worse, which I also expected. I am pretty sure that either the spark is too weak or else it gets too little fuel in the initial phase of WOT. If it was too much fuel, then keeping the throttle open should have it initially keep up and accelerating. But if I keep it open, then it dies down. Unless it is above 3500 then it just accelerates.

Changing things one at a time is the right way to go of course.

But before that, does the motor have good compression? Do a test.



Hmm interesting. I have not tested that, as I do not own a compression tester, but I will look and see how expensive they are and perhaps then do a compression test.

Wildgoose Chase Moto Guzzi

Re: 850 T3 Cali rough between 2000-3500
« Reply #3 on: May 24, 2022, 06:53:18 AM »

Online Dave Swanson

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • *
  • Posts: 3747
  • Northern Illinois USA
Re: 850 T3 Cali rough between 2000-3500
« Reply #4 on: May 24, 2022, 07:21:25 AM »
I agree with the prior posts.  Take your time and do a proper tune up and carb balance.  I would also recommend replacement of the distributor springs.  Your old ones are most likely stretched out.
Dave Swanson - Northern IL
1935 GTS
1968 V700
1973 V7 Sport
1974 Eldo
1977 Convert
1977 Lemans 1.2
1980 T3 California
1993 1000S - Sparklehorse
2004 V11S - Eraldo-ized
2016 Griso SE - Beetle-ized
2021 V7-850 Stone Centenario
2022 V85TT Guardia d'Onore

MGNOC L-780

Offline lucian

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • *
  • Posts: 3135
  • Location: Maine, Ayuh
Re: 850 T3 Cali rough between 2000-3500
« Reply #5 on: May 24, 2022, 07:44:26 AM »
Check the rubber seals on the bottom of the choke plungers, they can be pricked out and flipped over, if they leak , even a little, it'll be way rich, How are the spark plugs looking?

Offline Adv_hoon

  • New Egg
  • *
  • Posts: 24
Re: 850 T3 Cali rough between 2000-3500
« Reply #6 on: May 24, 2022, 01:52:56 PM »
I agree with the prior posts.  Take your time and do a proper tune up and carb balance.  I would also recommend replacement of the distributor springs.  Your old ones are most likely stretched out.

That might be a good point with the springs. I have not disassembled or checked the points yet, but I was told that it had a service less than 500km's ago and I can see that some of the parts surrounding the distributor looks brand new. But I will look at the springs when I check the points.

Check the rubber seals on the bottom of the choke plungers, they can be pricked out and flipped over, if they leak , even a little, it'll be way rich, How are the spark plugs looking?

Hmm I read about the choke plungers as a potential for issues, so I will check those as well, but I am pretty convinced that it is lean in the midrange and not rich. On the overrun once past 3500 it does sound a little rich though - so worth a look to see. Thanks for the tip.

The plugs actually look somewhat "normal" at least the left cylinder. The right one had not colored as much after I cleaned them so I expect this to be the one miss-firing from time to time.

Offline Adv_hoon

  • New Egg
  • *
  • Posts: 24
Re: 850 T3 Cali rough between 2000-3500
« Reply #7 on: May 24, 2022, 01:58:29 PM »
The slides from carbs looked very worn to me, but perhaps this is normal wear?




Online moto

  • Gaggle Mentor
  • ****
  • *
  • *
  • *
  • *
  • Posts: 574
  • Potrebbe andare peggio, potrebbe piovere!
  • Location: Madison, WI
Re: 850 T3 Cali rough between 2000-3500
« Reply #8 on: May 24, 2022, 06:57:26 PM »
The slides from carbs looked very worn to me, but perhaps this is normal wear?

[img]

It's hard to say without seeing how deep the scoring is, but I doubt this is the problem. Dave Richardson (in Guzziology) pointed out that the large flat sealing area of the VHB carb makes them much more resilient to scoring than round slides. If you wanted, you could sand the faces, I suggest. But I wouldn't bother.

If you can isolate which cylinder is dropping out, the carb slides are extremely easy to switch side-to-side to see if the problem follows them.

I'm eager to read what you find out when you get back to the problem.
850 T-3
Griso 1100 corretto
Italjet Buccaneer 250 (ex-SSR)
credit for 2500+ postings lost in the database meltdown of Feb 9, 2020

Offline s1120

  • Gaggle Hero
  • *****
  • Posts: 1861
Re: 850 T3 Cali rough between 2000-3500
« Reply #9 on: May 25, 2022, 05:10:26 AM »
That might be a good point with the springs. I have not disassembled or checked the points yet, but I was told that it had a service less than 500km's ago and I can see that some of the parts surrounding the distributor looks brand new. But I will look at the springs when I check the points.



Ahhh.  OK, we got something here..  So has the bike ran this way since you got it? If so sounds like someone was chasing this issue, or caused it. Have you been into the dist yet? Being you know someone was in there, and replaced stuff, I would go in, and make sure they did it right. Are the points set right?, it the timing right? is the advance working as it should? Looks for other new changed components also. Is the coil new? Did they leave a loose wire, or forgot a ground? You have no idea who replaced those parts, or their skill level. Id would check that out first.
Paul B

Offline Adv_hoon

  • New Egg
  • *
  • Posts: 24
Re: 850 T3 Cali rough between 2000-3500
« Reply #10 on: May 27, 2022, 02:54:52 AM »
It's hard to say without seeing how deep the scoring is, but I doubt this is the problem. Dave Richardson (in Guzziology) pointed out that the large flat sealing area of the VHB carb makes them much more resilient to scoring than round slides. If you wanted, you could sand the faces, I suggest. But I wouldn't bother.

If you can isolate which cylinder is dropping out, the carb slides are extremely easy to switch side-to-side to see if the problem follows them.

I'm eager to read what you find out when you get back to the problem.

I went ahead and sanded the slides on a piece of glass with 800 grit. They came out like new. My initial thought was that sanding them would make them seal even worse as they would be "smaller". But then of course I realized that they are sealed by vacuum from the engine so sanding them down actually makes sense. Thanks a lot for the tip.

Ahhh.  OK, we got something here..  So has the bike ran this way since you got it? If so sounds like someone was chasing this issue, or caused it. Have you been into the dist yet? Being you know someone was in there, and replaced stuff, I would go in, and make sure they did it right. Are the points set right?, it the timing right? is the advance working as it should? Looks for other new changed components also. Is the coil new? Did they leave a loose wire, or forgot a ground? You have no idea who replaced those parts, or their skill level. Id would check that out first.

It ran somewhat bad - but got worse. I was told that it was a reputable shop that had done the service. But I found some things.

Yesterday I worked on the bike and got it running a lot better. First I checked the points. They were brand new but I found that the left cylinder had a little bit too narrow gap, which I adjusted.

Then I disassembled the carbs and inspected jets and everything. I found some marks in the needle of the right hand side carb - so I have ordered a new one. I also found that the carbs had 130 jets in them instead of the 120 that I believe should be the standard size to a 850 T3 California. Then I sanded the slides on a piece of glass to remove the scoring marks and finally assembled everything.

I then started up the engine to verify two things; charging and ignition timing.

First of all the charging seems to work but in my opinion a good 0.5 volts too low at all points. Idling there is only around 11.5 - 11.6 volt on the battery. Above 2k there is around 12.3-12.6 and somewhere above 3k there is 13.4 or something like that. So it charges - but those values seems 0.5 volt too low? Any ideas on what could cause this? It is a bosch system but all parts appear very old.

Running with the "low-voltage" theory I also found that the voltage at the coils are around 1 volt lower than at the battery. Meaning that at idle they only see around 10.5 volts. On my other bike, a KZ650, I wired a relay with voltage directly from the battery to counter this. Is there a write-up or guide for this mod on old guzzi's or will I have to study a wiring diagram to figure out which wires turn on the power for the coils?

This brings me to the theory of a cylinder dropping out. I am quite sure it was caused by low voltage. I had been doing a lot of tinkering, starting the bike up, idling etc. and given the weak charging at low rpm's I believe that I had run the battery down to a low charge which combined with the low voltage at the coils crossed a threshold for one of them. Back when it cut out, I could get it to come back at above 3 - 3500 which correlates with where the charging delivers some proper voltage.

With a charged battery it ran without dropping any cylinders.

Finally I looked at the ignition. I could not find any marks with letters or numbers as mentioned in the manual I had. But I found clear white marks on the teeth of the flywheel which by inspection through the spark plug holes matched with TDC. Going by these the ignition was retarded. I advanced the ignition to make the right had cylinder fire 2 degrees before TDC (which I believe is the correct position). Checking the left hand cylinder it then fired 4-5 degrees advanced. I went for a test drive and had to retard it slightly as I could make the left cylinder detonate if I was really mean to it. But when I have a bit more time I think I will modify the points a bit so I can make both cylinders fire at the correct time.

The conclusion is that it drives a lot better but still has a rough spot between 2-3500. First remedy for this is to get 120 jets and a new needle for right hand side. Then there is also some work to do with charging and I also find it a bit difficult to keep running when cold. The choke only works to get it running, then immediately it has to be turned off in order to not kill it again. But it has to run for quite a while before it is able to idle by itself?

Online Frenchfrog

  • Gosling
  • ***
  • Posts: 463
Re: 850 T3 Cali rough between 2000-3500
« Reply #11 on: May 27, 2022, 06:36:44 AM »
If the needles are worn then the  jets are very likely to be too, especially the needle ones. I'd get new mains, atomisers ( needle jets ) and go from there.

Offline s1120

  • Gaggle Hero
  • *****
  • Posts: 1861
Re: 850 T3 Cali rough between 2000-3500
« Reply #12 on: May 27, 2022, 07:38:04 AM »
If the jets/needles don't fix it, at least you will be going into this with a known stock baseline to tune from. As for all your charging/voltage issues. Have you gone through and cleaned all the wire connections, and grounds? Its a good thing to do on ALL old vehicles, and Guzzi's more so.
Paul B

Online chuck peterson

  • Gaggle Hero
  • *****
  • *
  • Posts: 4803
  • Location: New Haven CT
Re: 850 T3 Cali rough between 2000-3500
« Reply #13 on: May 27, 2022, 07:48:13 AM »
On your voltage readings…if the headlight was on, your pretty good. If the headlight was off your a bit low..there is an adjustable voltage reg available, but clean/scrape/smear your grounds

On the point gap…you found one of them on the narrower side and adjusted to spec…but later you suggested adjusting the point gap for better timing…bingo! That’s a common issue w dual plate points.

On the change of jets…have you figured out if its an 850cc or 1000cc? Could be an issue

Good luck! Don’t believe anything from 2000 miles away over the internet….
"I'd like to thank all my friends who have kept my Guzzi's going, but mostly...TOMB."
150k on Verts
750 Nevada
400f
R5 Yammie
BV250
4x 1976 Moto Demm Smily,, now 5, oops now 6, oops now 7
1980 SP1000 in little bits and pieces

Offline Adv_hoon

  • New Egg
  • *
  • Posts: 24
Re: 850 T3 Cali rough between 2000-3500
« Reply #14 on: May 27, 2022, 08:33:11 AM »
If the needles are worn then the  jets are very likely to be too, especially the needle ones. I'd get new mains, atomisers ( needle jets ) and go from there.

It was not worn. It looked more like someone had dropped it. It had some marks on the tip. I sanded it a bit to smooth it out, but I have ordered a new one.

If the jets/needles don't fix it, at least you will be going into this with a known stock baseline to tune from. As for all your charging/voltage issues. Have you gone through and cleaned all the wire connections, and grounds? Its a good thing to do on ALL old vehicles, and Guzzi's more so.

No unfortunately I think I need to methodically do this. All of them looks quite old/worn, so it sure as hell won't hurt to do so. Apart from the rather boring work :)

On your voltage readings…if the headlight was on, your pretty good. If the headlight was off your a bit low..there is an adjustable voltage reg available, but clean/scrape/smear your grounds

On the point gap…you found one of them on the narrower side and adjusted to spec…but later you suggested adjusting the point gap for better timing…bingo! That’s a common issue w dual plate points.

On the change of jets…have you figured out if its an 850cc or 1000cc? Could be an issue

Good luck! Don’t believe anything from 2000 miles away over the internet….

Okay, interesting. It was with the headlight on. I will do the boring work of going through the wiring and cleaning the connections, but otherwise I will probably look into a voltage regulator.

Yes, regarding the points and timing it seems like there is a few degrees of difference between them, so I will surely modify them to have both cylinders fire at the correct time.

No I have not found out whether it is 1000cc. To the best of my knowledge there is no visual way to determine without taking the heads off. So my thinking is that if it runs even worse with 120 jets, and hence totally standard spec parts in the carbs, then it is probably 950/1000cc. At least I then have a baseline of where it should be running well if it is 850. I still need to adjust the valves and do the trick on points for proper timing - but then it should run rather good given it is 850 and not 950cc. Time will tell.

Online chuck peterson

  • Gaggle Hero
  • *****
  • *
  • Posts: 4803
  • Location: New Haven CT
Re: 850 T3 Cali rough between 2000-3500
« Reply #15 on: May 27, 2022, 09:00:00 AM »
Rereading your post…are you snap opening all the way to WFO at 2500 rpm? That might be a bit of a challenge for a heavy flywheel Guzzi ..my fuel injection motor protests at that…

Drop two gears, try that wfo thing while running 6k rpm.
"I'd like to thank all my friends who have kept my Guzzi's going, but mostly...TOMB."
150k on Verts
750 Nevada
400f
R5 Yammie
BV250
4x 1976 Moto Demm Smily,, now 5, oops now 6, oops now 7
1980 SP1000 in little bits and pieces

Offline Adv_hoon

  • New Egg
  • *
  • Posts: 24
Re: 850 T3 Cali rough between 2000-3500
« Reply #16 on: May 27, 2022, 10:45:54 AM »
Rereading your post…are you snap opening all the way to WFO at 2500 rpm? That might be a bit of a challenge for a heavy flywheel Guzzi ..my fuel injection motor protests at that…

Drop two gears, try that wfo thing while running 6k rpm.

Yes, there are two parts to it. It runs roughly in that rep-range and one of the symptoms is that if I open the throttle fully at 2500 rpm then it bogs down. I can understand if it would struggle and not be happy with it in top gear. But it completely bogs down, which in my opinion points to an issue with carburation. If I open the throttle fully from 2500 in first or second gear I would expect it to leap forward, not dye down. I can understand in the upper gears, but there is something not working correctly.

***Wildguzzi Official Logo High Quality 5 Color Window Decals Back In Stock***
Shipping in USA Only. Awesome quality. Back by popular demand. All proceeds go back into the forum.
http://www.wildguzzi.com/Products/products.htm
Advertise Here
 

20 Ounce Stainless Steel Double Insulated Tumbler with donation credit
Buy a quality tumbler and support the forum at the same time!
Better than a YETI! BPA and Lead free.
Advertise Here