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Ideal 850T3 setup

Choirboy

Choirboy

Tuned and Synch'ed
Joined
Jul 16, 2010
Messages
26
Location
SE Iowa
Hello to all after a long absence! I am looking for advice as to what should be done to my 20,000 mile 850T3 FB "while I have it apart." Life situation prevented me from getting it back on the road two years ago, but things have improved and now is the time.
Taking some risky advice I drove it for several thousand miles on the original chrome bores. I am sure I didn't do any damage (popped a cylinder off the other day and the chrome looks perfect, I'm hoping the other looks as good) but want to get rid of the chrome bores before my luck changes. The bike ran ok, but in hot weather while loaded it would ping a lot.
I ride equal time solo unloaded and two up with camping gear. Also about equal time 45-55mph backroads and whatever the flow of traffic is on I-80 or I-90; between 70 and 80mph. I frequently travel in very rural areas and am frequently faced with the choice of 86 octane fuel or nothing. I'm a fairly conservative rider but I'm not afraid to really RUN the bike when needed.
Since the engine has so few miles for a Guzzi, I was originally planning on getting the original cylinders nikasil plated (someone recomended Millennium in Wisconsin to me) and putting in all new seals to stop the obnoxious oil leaking. Then I was talking to my friend Howard who claims his 850 not only has more power with his B10 cam, but also gets better fuel mileage, and he thought the next hotter cam might get better mileage yet, at least on the interstate. Since I live in the midwest superslab driving is a near requirement for any vacation... the thought of not only improving power but also fuel mileage is very appealing to me.
I guess the point of this thread is I'm looking for advice from more experienced people to help me get this engine right the first time. I don't want to waste money doing unnecessary things but I don't want to have to do things twice because I'm unhappy with the result.
In brief: Looking for a do-all bike that will see hot weather and camping loads, won't ping on crap gas, and will have enough power to be fun yet get 40 or more mpg cruising.
My current thoughts are stock pistons, nikasil plated original cylinders, b10 or slightly hotter cam, tight squish, and possibly dual plugging the heads (again, don't always have access to high octane). I know a lot of people want the 950 cylinders for the grunt and bigger carbs for the top end power, is it worth the dollars?
Any advice? I appreciate all viewpoints! Thanks!
 
The 850 size is a sweat engine, keep it that way. Going to 950 or so will just increase vibration without all that much power. To my knowledge, the 850T3 was not chrome bored, mine wasn't, but it isn't nikisil either, that came out later. Going to nikisil is a good thing, as is the B10 cam. Hotter cam may make the engine too radical for driveability.

Go into the timing chest and put in a good cam chain tensioner. The one from MG cycle serves well. As you said, since she is apart, replace every seal and gasket. Doing the transmission seals, o-rings, and replacing the shift spring wouldn't be a bad idea either. While you are in the transmission, shimming the shift drum will improve shifting. Pete Roper has some excellent write ups on the web for doing this task, or you could just send it to Charley Cole at Zydeco Racing and have him do the job. While she is apart, update the clutch to the 4mm spline type, that way you won't need to take it apart again at 40,000 miles to replace the worn hub gear, because it will fail at about that mileage.

If you want to reduce pinging, the dual plug is an option, but re-adjusting the timing can be tricky. Harper's once had a set of thicker base gaskets available back in the 80s to reduce pinging on low octane fuel. They may still have these available.
 
For what it is worth: The closer you stay to stock the less trouble you will have. Once you modify one component it effects how all others perform and generally begins a cascade of modifications and expense.

That being said: Red Dog (74 850 T shown) has an unknown ungodly amount of miles with original stock chrome bores that are starting to show signs of wear but do not smoke. It has points & cond ignition, original jetted carbs (for a T) and stock cam. I ride mainly solo but do on occasion load her up for extended camping. I average 70 mph for normal riding but when riding with others many times I have to do the cruiser crawl at 50-60 mph. She has no problem "doing the ton" or above and is perfectly happy running errands in town. I use mid octane gas and every 10 tanks or so throw in a couple of shakes of Marvel Mystery oil. I don't believe in or use oil additives. It is by far the best "overall" bike I have ever had the pleasure to share a life with. I would leave for the west coast on her tomorrow and not think twice about it.

For the style of riding you describe I advise stay as close to stock as possible. If the engine is off then re-seal & re-gasket, check timing chain, check clutches, check u-joint & bearing, look at all the little rubber bushings and mounts, tighten linkage etc.

The only real modification might be to rejet the carbs as the T3 carbs have smaller jets than the early T from what I understand. I would also replace the needle & seat & float and make sure the float is set correctly. As far as the pinging goes either learn how to properly adjust valves, set up the points (if you still have them) and get the timing right or pay a good Guzzi wrench to do it & the carbs for you. Less restrictive mufflers will also make a big difference over the stock units. Properly set up your machine will lope around town or cruise at 80mph with equal beauty.

Just my opinion and we all know what they are worth.
Trout
 
Just noticed that you have both an Ambassador & a T3.

Ever consider setting the Ambassador up for all you touring/camping needs & to run on low octane? My wife & I logged many thousands of miles on ours in the 70's. That would leave the T3 for some performance mods that may satisfy the go fast urge.

It is a difficult thing to get one bike to be a hi fuel mileage cruiser & a responsive spine tingler especially older pre-tech machines. It can be done but does require a good amount of tinkering time to work it out. I have always felt that out of all the bikes being produced Guzzi was the only one who actually achieved this.

In John's post he liked the B10 cam so I would say go with it while you've got the engine apart because any modifications needed from that point won't require the engine to be pulled back out. Carbs, ignition, head work can all be done easily enough sitting on a bucket.

More than anything else have fun doing it.
Trout
 
I don't know if you can still get them but in a previous rebuild of my T the timing chain was replaced with gears. You will never have to replace the chain again. I have previously been told to not switch octanes from fill to fill, so go for the low octane, get it tuned for that and stick with it (others may have better info on this.) You might want to consider gas shocks for the rear that are adjustable for when you change the load on the bike.
 
guzzigirl said:
I don't know if you can still get them but in a previous rebuild of my T the timing chain was replaced with gears. You will never have to replace the chain again. I have previously been told to not switch octanes from fill to fill, so go for the low octane, get it tuned for that and stick with it (others may have better info on this.) You might want to consider gas shocks for the rear that are adjustable for when you change the load on the bike.
Click to expand...

If you can find steel gears for a tonti engine that would be good. I think Old Jock has a source for them, but they aren't cheap. Some of the aluminum gear sets can cause problems down the road due to excessive wear of the aluminum and it being deposited in the crankshaft oil passages which causes oil starvation at the mains and conrods.
 
I don't know if you can still get them but in a previous rebuild of my T the timing chain was replaced with gears. You will never have to replace the chain again.
Click to expand...

Timing gears are a real potential flame war so this is my own opinion for what it is worth.

Personally I wouldn't bother. The all aluminum gears can be trouble - from Pete Roper's experience sometimes they work fine for virtually forever, sometimes they instantly self-destruct basically destroying the engine.

The set with the steel crankshaft gear is, at least, from an engineering perspective the correct way to do it.

The longer view is that timing gears don't give any more performance (I measured it back to back on the dyno and there was nothing there). The chain, when fitted with the (Valtek or Agostini) aftermarket tensioner as John suggested, lasts virtually forever.

To me it is a waste of money with potential problems that may or may not bite you.

Reducing the compression is the last ditch method to getting rid of detonation - it will reduce performance and mileage. I am a bit surprized that a T3 would be pinging but it really is dependent on your local gas. Assuming carburetion is stock, I'd check the timing before I did anything and retard it until the detonation goes away.

As John suggests twin plugging will help a lot - you should be able to knock the advance back at least 6 degrees. You will have to recurve the distributor to suit. With the round heads it is not too hard to do.

I'd fit a Dyna at the same time as the points on the guzzi are a pain to set up properly and can never be fully optimized - when you get the timing right on both sides, the dwell is wrong on at least one set of points (in the twin point set-up). The Dyna is not perfect but is available, relatively cheap and with 5 Ohm coils reliable -keep the points plate in your toolkit in case of failure to get you home.
 
I think mine are the steel gears and I have had no problems with them. Noted that people have had problems with them. I certainly would not recommend aluminum - the potential for wear would defeat the purpose, surely?
 
When the time comes I recommend the following for less fuss:

Starter: When the Bosch starts giving you trouble get rid of it and go for a Valeo that uses less amperage.

Battery: An Odyssey battery has been bullet proof in my experience. A 925 for the Bosch starter or a 625 for the Valeo. The 625 is only $5 more that the Yuasa battery for the B11 - a bargain!

Points: Hate'm - Saches makes an ignition system that eliminates the distributor available at EME.

Switches: Once those OE units are start giving you trouble MG Cycle has some good substitutes.

And for better acceleration, a set of PHF DellOrtos. The pumpers help a little.
 
Thanks for the advice so far! Keep it coming!
I do own an Ambassador but due to a long and depressing story I don't wish to go into, it is out of commission at the moment. With funds to only fix one bike and a look at our upcoming trip plans I decided the T3 is the one to get running now. I'm not necessarily looking for a "spine-tingler" of a bike, just one that doesn't get left completely in the dust! My Ambo gets left in the dust!
I also am surprised that the T3 pinged so much, and to be honest there could have been several fixable reasons for this; when I was driving the T3 a lot I didn't have time/space/expertise/money to approach the problem so I just drove very conservatively. But, since I'm going to have it apart, I want to do anything I can to prevent the problem from returning when the bike gets on the road.
Two questions:
1. Is it necessary to both set a tight squish and also to twin plug? I'm not opposed to doing both if it will be of help, but if not perhaps I could just do a tight squish and save some machine work?
2. Will the stock T3 carbs work with a B10 cam, or will I actually lose performance with the hotter cam and restrictive carbs? As carbs are a bit pricey and can be changed without opening up the engine, I'd hoped to do any inside work now and continue to upgrade as money becomes available.
 
Stock carbs with the B10 certainly won't be ideal but the bike will run. If you go that route I would not expect any improvement in any area: performance, fuel mileage, pinging etc. Personally I wouldn't do it unless I knew that my budget would allow the necessary carb changes in the very near future. Knowing me I'd be riding around thinking "I spent $300.00 on a cam for this?!!!" Performance may actually drop off with stock carbs.

I'm not up on current slang but if setting a "tight squish" is increasing compression by shaving the head or using thinner gaskets you will be working at cross odds with the ping problem especially if low octane fuel is part of the problem. Increasing compression with poor fuel means the timing will have to be set back which makes Jack a Dull Boy. Add a B10 cam in this mix and well....... I have no experience with dual plugs on older machines. I remember when it was first happening it seemed that the all out performance guys felt it was worth the bucks but a lot of "regular" riders I talked to didn't think it was a good investment.

Trout
 
I was wondering if the B10 would work with stock carbs... but carbs can be done at a later time without removing/disassembling the engine, so maybe it would be worth it even with no short term gain.

I was under the impression that having a proper squish (something around .040 if I recall) would decrease the chance of pinging? Am I mistaken? Has anyone out there dual plugged a round fin and get the squish at around .040?
 
The B10 should work fine with the stock carbs, it did "in the day." As for modifying the squish and dual plugging, that is redundant. I'd say you should be fine with stock clearance if you dual plug, or don't dual plug and just run it. Put in premium and you should be fine, and downshift if you detect pinging.
 
The pinging problem could almost be entirely due to your carbs & manifolds.
Considering the age of the bike and I assume nothing of the following has been done before.

Replace every carby gasket, 'O' ring, rubber manifolds etc. Any air leaks will for a start make it so hard to tune accurately. I took this advice and did it to my old Calli II, what a difference. Check the needle isn't worn and the needle jet ovalized, they will cause the bike to eventually run rich (too rich) and kill mid range.

Also with pipes and K&N filters it was so lean it could hardly pull the skin off a rice pudding.
Local dealer told me Dellorto didn't make alternative jet sizes for the 30mm square slide, but Mikuni do :D
Yamaha XJ 550/650/750/900 from the 80's used different pitch thread main jets to other Mikuni's.
Got heaps more mid range power, 20kph more top speed and better economy.
 
All jet sizes are available, at least in the US http://www.herdan.com/ If you aren't sure of the jet for the application, call them and they will get you the correct size thread jet. The square slide uses the same thread jet for both the main and pilot. The newer round slide has a larger thread jet for the main.
 
I don't doubt that much of my pinging was due to the carbs, and I plan to fix that when the motor goes back together. Thanks for all the info/opinions so far, it has been great!
Is the B10 the only cam I should be looking at, or is there a better option?
 
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