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850T bottom end

Sporticus

Just got it firing!
Joined
Aug 25, 2013
Messages
23
Location
Western Massachusetts
Can anyone tell me what a bad rod bearing sounds like? I have a rap at higher RPMs, and it feels like something is hitting the inside the rocker box cover. This has been going on for about 1,000 miles. Thanks for any insight.

Scott
 
Can anyone tell me what a bad rod bearing sounds like? I have a rap at higher RPMs, and it feels like something is hitting the inside the rocker box cover. This has been going on for about 1,000 miles. Thanks for any insight.

Scott

Not to be rude but why don't you whip off the valve covers and sump and as Pete Roper used to say have a squizz. Asking the forum to diagnose your motor over the internets is really kind of hopeful. Frankly it could be anything from badly adjusted valves to catastrophic big end failure.

The guzzi engine is one of the easiest motors to work on so dig in. It takes about half an hour to remove a cylinder going slow.

And why did you drive it for 1000 miles when it was making a nasty noise?
 
It took some time to take it apart. Excessive big end connecting rod play. My manual sucks. Can anyone tell me if the bearing shells can be replaced with the engine in frame (before I drop the oil pan). I believe this happened because it ran low on oil. I would have expected something bad to happen in the combustion chamber before the bottom end took a dive.
 
You need to drop the pan. Also be sure to check the condition of the crank. If the shells went bad, it is possible the crank needs attention. If you need dimensions for the crank journal, let us know. Also keep the rod and caps together and matched.
 
Into the bottom end I went (with engine still in frame). The repair manual I have is horrible and doesn't have the answers. The oil sump (name?), a/k/a the thing that the filter bolts to, stands between me and the crankshaft. Since I'm lying on my back on the shop floor, I can't get a great look. How does this thing come off? I fear that the front engine cover has to come off to access bolt heads. Can someone tell me I'm wrong? Thanks for any help!

Scott
 

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Into the bottom end I went (with engine still in frame). The repair manual I have is horrible and doesn't have the answers. The oil sump (name?), a/k/a the thing that the filter bolts to, stands between me and the crankshaft. Since I'm lying on my back on the shop floor, I can't get a great look. How does this thing come off? I fear that the front engine cover has to come off to access bolt heads. Can someone tell me I'm wrong? Thanks for any help!

Scott


Not only do you need to pull the front cover, you need to remove the timing chain. Find a Haynes manual for your bike. The fellows that write them, actuall do the procedures. They aren't a knoc off from teh factory manual. Do note, you need a hardened pin to be able to remove the Bosch rotor. Without it, you can't. If you use a soft pin, it can bend and lodge in the end of the crank and that is a whole other problem. http://www.mgcycle.com/index.php?main_page=product_info&cPath=80&products_id=4631 While you are in there, a new cam chain and tensioner would be in order. The stock tensioner on a T are a joke. See http://www.mgcycle.com/index.php?ma...iption=1&keyword=cam+chain+tensioner&x=18&y=5 and http://www.mgcycle.com/index.php?main_page=product_info&cPath=68_126&products_id=978 Be sure to align timing marks before you pull the chain and gears. They all come off and on at the same time.

If it is something you don't want to get into, I'm sure the guys at A-Js in Gill can probably help you.
 
This may not help but ......I have just ( within 500km's ) done up my 74 850t ,inc new bearing shells and crank grind , and when 1st started is as quiet as a mouse but within 30 seconds I get a light clonking that is really hard to pin point , to deep for valve clearance , and it stays there until I go for a ride , good oil pressure , but go for a quick ride , 2-3 km's and the noise is gone and stays gone until the engine cools completely , then the whole cycle starts again upon the next cold start . I probly have my idle set a bit low ( below 500rpm ) as when hot after a ride the idle drops a bit and the oil pressure light flickers a bit for a minute then the idle picks up a bit and the light stays off . carbs a well balanced ( mercury Colum gauges ).I will speed up the idle when its a bit more run in ..... just cant be bothered at the mo as I would like to use the gauges when doing so as I like to get things spot on.......another thing is that I have no valve noise but I have checked the clearances both cold and hot , the cold clearance is spot on ( measured with feelers ) and the hot just got the wiggle test ( side of the road ) but there is still clearance.mmmmmm . Oh , I am using Valvoline XLD oil but I intend to go to Penright synthetic ..... unless there is a reason not to use synthetic oil .
 
500 RPM is much too low. Should be 900 t0 1.000 RPM at idle. That low may result in loss of oil pressure (you see the light flickering) which will damage the bottom end. Idle sync isn't critical. Get the idle up now. Just twist the grip to open the slides then turn each screw in an equal amount. I may not be perfect, but close enough until you can use the carb sticks. I am a little concerned abut you noise that starts then goes away. Can't be sure if it is a clearance issue (too much) or not enough oil pressure. Once you get a few miles on and the piston rings seated by all means switch over to synthetic.
 
500 RPM is much too low. Should be 900 t0 1.000 RPM at idle. That low may result in loss of oil pressure (you see the light flickering) which will damage the bottom end. Idle sync isn't critical. Get the idle up now. Just twist the grip to open the slides then turn each screw in an equal amount. I may not be perfect, but close enough until you can use the carb sticks. I am a little concerned abut you noise that starts then goes away. Can't be sure if it is a clearance issue (too much) or not enough oil pressure. Once you get a few miles on and the piston rings seated by all means switch over to synthetic.


Yeah I know the idle is to slow but 900 / 1000 rpm seemed to fast ,:)
 
Sorry John , I didn't mean to imply I was disagreeing with you. I just feel that if I can get the bike to idle sweet as at 7-800 rpm , 1000rpm sounds to fast . I haven't checked the oil pressure at all but will do so as I have good reason to believe my big ends may be a bit suss, I bought the bike after some penis fingered ( #ucked everything he touched ) bush mechanic had charged the owner a mint to rebuild the engine and he hadn't bothered to clean out the crank after grinding the big ends ( to 30 thou under ) , fortunately it didn't get to far before the new pistons seized in the undersized bores ( resleeved with steel liners ) and being as the big end looked ok ( I was to scared to go anywhere near it with a micrometer ) and 30 thou was the last undersize I chucked in a new set of shells and crossed my fingers . Oh and the oil pressure sender has a cracking pressure of 15 psi ( according to the catalogue ).
Thanks John
Hamish
 
A Guzzi engine isn't a Harley engine. It needs to turn a higher RPM. Low RPM results in low oil pressure and the alternator doesn't kick in either. The oil pressure is the critical factor. Those large plain bearings need good oil flow to keep them cool and reduce wear.
 
A Guzzi engine isn't a Harley engine. It needs to turn a higher RPM. Low RPM results in low oil pressure and the alternator doesn't kick in either. The oil pressure is the critical factor. Those large plain bearings need good oil flow to keep them cool and reduce wear.
I hear what your saying John and you sure are right about the alt , mine doesn't kick in until about 1500 rpm. I will set the idle at 900rpm and check oil pressure and just get used to it :). I have some other issues with the gearbox I would appreciate your input on .... new thread
Thanks John
Hamish
 
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