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PostPosted: Fri May 25, 2018 3:28 am 
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Around the block

Joined: Tue Nov 07, 2017 3:25 pm
Posts: 51
Country: Portugal
Suzuki 2-Strokes: GP125, GT380
I finally managed to complete the 380 & take it out for a ride. It starts 1st or 2nd kick normally.
On a previous post I queried excessive smoke so drained the crankcases through the 3 bolts. Only a few drops of oil came out.

First I took a ride along the internal roads and the bike smokes considerably to the extent that you can't see anything behind you. It also throws black oil out of all 3 exhausts.
After a few km I took the bike onto the motorway but the smoke screen is excessive no matter what gear or RPM you are at. I accelerated through the gears but when I changed into 4th it started spluttering/jerking & missing as if not firing on all cylinders.
It started loosing speed & I had to reduce to 2nd & 50kph to maintain it moving until I could get it off the motorway. On a slight uphill it lost more power & I had to resort to 1st gear.
I stopped when off the motorway but kept it running & revved it at which time I heard it firing on all cylinders & took it home (approx 3km). Once home I removed the plugs but found these to have a tan colour & no oil residue (seemed normal). My sons car that was travelling behind me was full of black oil.
The bike runs on Valvoline mineral 2 stroke oil (as it has always run on) fed through the CCI, 95 Octane pump fuel (was fresh), has a Newtronic ignition and all sett as per the manual (timing, pump & carbs) .
The oil lines & check vales have been checked for leaks (filled with oil & hung). These are perfect no leaks.

Can anyone please advise on possible causes for the excess smoke, black oil being spat out of the exhausts & the missfiring.

Many Thanks
Carlos


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PostPosted: Fri May 25, 2018 7:57 am 
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Moto GP
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Joined: Mon Nov 03, 2008 10:47 am
Posts: 6087
Location: Illinois
Makes me wonder if the exhausts are full of oil from the prior owner. Pull the baffles and see if the wadding is chocked with oil.


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PostPosted: Fri May 25, 2018 8:09 am 
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Moto GP
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Joined: Mon Dec 13, 2010 4:32 pm
Posts: 3570
Location: southwestern Pennsylvania
Country: USA
Suzuki 2-Strokes: 69 T350 thru 75 GT750
Did you or a PO work on the oil pump?

Its possible to put the oil pump actuator arm on 180 degrees out of the correct position. This gives you maximum oil pump output at idle.

I had this problem with a GT750 & have a topic on how to figure out the correct position.
(Some of the pics were trashed by Photobucket. I posted replacement pics at the end of the topic.)
http://www.suzuki2strokes.com/forum/viewtopic.php?f=2&t=11662&hilit=oil+pump&start=15

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BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 73 project
T350 69, 71 & 72 project
T250 72
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE


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PostPosted: Fri May 25, 2018 11:35 am 
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Yeah Man, the Interstate

Joined: Tue Mar 10, 2015 12:35 pm
Posts: 524
Location: Wales
Country: WALES
Suzuki 2-Strokes: suzuki gt 550j
IMHO the problem appears to be the exhaust's. If too much oil was being fed into the motor the plugs would be black in colour and would eventually stop the motor. To me it all points to severely oiled up exhaust's burning off the oil with use. The power loss will be down to the fact that burnt gas not being able to escape. I would agree with removing baffles. If there is wadding still on there remove it and put it in the bin. Remove all the carbon and oil from the baffles with a blowtorch and put them back in. Take it for a hard ride but I would stay off the motorway

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98 carb Blackbird and GT550j


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PostPosted: Fri May 25, 2018 1:12 pm 
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Novice racer
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Joined: Wed Jan 18, 2012 8:01 pm
Posts: 952
Location: North of Albany, NY
Country: USA
Suzuki 2-Strokes: T500R (now), T500M (40 yrs ago)
Also consider you may have an over rich mixture. You will have excessive smoke as well as a loss of power.

When you misfire, the engine may be "4-stroking". This term means instead of firing every engine rotation, it is firing ever second (or third, or...). When this happens, the fuel charge from the previous cycle doesn't clear the cylinder, leaving extra fuel (and oil) from the previous misfire. You will end up with a lot of oily smoke.

Telltale behavior of rich 4-stroking is feeling like it is misfiring, a bubbly, gurgling sound to the engine note. Distinctly different from a lean mixture, which feels more like just a drop in power, where the engine just doesn't seem to give all that it could.

I don't know the GT380 well, but if it has Mikuni carbs, confirm it has the correct genuine Mikuni jets, the choke plungers are in good condition and seating properly, slides are installed properly and are synchronized, and float heights are correct.


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PostPosted: Sat May 26, 2018 2:21 am 
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To the on ramp
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Joined: Sun Jul 13, 2014 7:55 pm
Posts: 282
Location: Greendale Vic, Australia
Country: Australia
Suzuki 2-Strokes: AS50, GS500, GT500, ex GSXR750 slabbie
Sounds very much like glugged-up oily exhausts to me. Pull out the baffles and clean them, and thoroughly clean out the exhausts.
I like to burn mine out, but that's not kind to chrome is it... there are chemical cleaners though.


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PostPosted: Tue May 29, 2018 12:16 pm 
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Expert racer

Joined: Wed Jul 10, 2013 12:04 pm
Posts: 1087
Country: England, UK
Suzuki 2-Strokes: FZ50, GP100, RG125 Gamma, GT380, Bandit 1200S
joolstacho wrote:
Sounds very much like glugged-up oily exhausts to me. Pull out the baffles and clean them, and thoroughly clean out the exhausts.
I like to burn mine out, but that's not kind to chrome is it... there are chemical cleaners though.

+1 on that. Incorrect mixture or massively over-oiling would be likely to leave tell-tale signs on the spark plugs. Masses of oil and smoke coming from the exhausts but no signs of that on the plugs would make me look at the pipes too.


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PostPosted: Wed May 30, 2018 1:12 am 
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Joined: Mon Dec 01, 2008 2:52 am
Posts: 1224
Location: Manchester, UK
If you have an old clutch cable or similar, use that to scour hard-baked carbon and crud from the inside of the pipes.

Cut the nipple off one end of the cable and fray the ends so it looks a bit like a small chimney-sweeps brush. Put the other nipple in the chuck of your electric drill, then stick the frayed end inside the pipe and go for it as much as you can, up and down the inside of the pipes.

I've found the worst build-up is usually in the two large outer (one-piece) exhausts, where the header pipe is welded to the silencer body. You often get an internal ring of carbon build-up which chokes performance, so pay special attention to that.

Don't worry too much about the small chambers around the removable baffles, the sections that are worst affected are the belly of the pipe and the headers.

Get a rubber mallet too, and give the pipes a good twatting along the welded seams. That can help dislodge big lumps.

You can also use a jetwash nozzle up both ends of the pipe (Pro tip: remove from the bike first :lol: )

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1976 GT380 - wounded by me, and sold on
2006 SV650S - killed by a patch of diesel and a kerb in Feb 2019
2017 SV650 AL7 - naked and unashamed


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PostPosted: Fri Jun 15, 2018 5:49 am 
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Around the block

Joined: Tue Nov 07, 2017 3:25 pm
Posts: 51
Country: Portugal
Suzuki 2-Strokes: GP125, GT380
Just a quick update of my findings.
I removed the exhausts and they weren't filled with oil as I expected. A minimal amount of oil came out whilst they were hanging. I also removed the baffles and there was minimal oil on the insulation. I have cleaned the chambers out with caustic soda but when washed out were pretty clean (relatively clean water came out). I didn't expect there to be much as the insulation and chambers have only done around 3000km from new.
I also drained the crankcases through the drain bolts at the base of the crank and minimal oil came out.

I have checked the oil pump and the lever is on the correct way. I stripped the pump and found that to be correct internally the 2 plungers/pistons were free and the top hardened rod with the slot facing inwards as it is supposed to be. There is a topic within this forum explaining how the pump should be and all was as explained.

I re-checked the plugs and although the colour seems correct (tan) there was a slight oil residue on all three.

I have also removed the carbs but didn't have enough time to check these out. I will do this on my next visit at the end of the month. These carbs have the correct factory jets with the mains being changed for larger units due to K&N filters and the expansion pipes.
I may install the GT550 carbs I have but will first need to clean them out and set them.

I checked the oil reservoir and found that for the amount of mileage I done (30km) the level had dropped by approximately 10mm which I feel may be excessive. The pump doesn't leak nor do the oil lines/check valves and was set as per the manual.

Some info about the bike - This has been in my possession from 1986 and had the centre big end go in a big way in 2013. At this time due to my financial situation (hasn't changed much since) the costs associated with the repairs were way out of my league and therefore I decided to get a motor from the breakers. This seems to be an 1975 Italian import. The motor was stripped and all clearances, limits, etc were checked against those given by the manufacturer. These were found to be within the service limits.
I never experienced any of these symptoms with the previous motor using the same pump, carbs and exhausts.
Due to working away from home the bike has only recently been completed and am very keen to get it going again.

Any further advice as to what the cause may be for the excessive smoke and black oil being spat out of the exhausts is greatly welcome.

When removing the exhausts the centre exhaust stud including part of the casting that holds this stud broke off. This stud had been helicoiled in by the previous owner and my assumption is that this may have weakened it. My question is as the motor is an aluminium casting can this be welded back?

Thanks
Carlos


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PostPosted: Fri Jun 15, 2018 7:37 am 
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Yeah Man, the Interstate

Joined: Tue Mar 10, 2015 12:35 pm
Posts: 524
Location: Wales
Country: WALES
Suzuki 2-Strokes: suzuki gt 550j
Couple of observations for you:
Your oil consumption is way to much can you source another pump. I had this happen to me once a mate following Mr had oil on his visor! I just replaced the pump and it solved the problem.
You say the engine is an Italian import which means it has a bigger capacity of 384cc compared to the standard 371 cc. It was made bigger for Italy because of import regs. How this affects your problem I'm not sure?
I would hold back putting the 550 carbs on until you solve this problem as it will just add anot her anomaly to the situation.

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98 carb Blackbird and GT550j


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PostPosted: Fri Jun 15, 2018 1:24 pm 
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To the on ramp
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Joined: Mon Jun 12, 2017 12:01 pm
Posts: 253
Location: Galveston County, Tx.
Country: USA
Suzuki 2-Strokes: '75 T500M since '93 Ridden it over 100,000 mi
GTandcbr wrote:
....Your oil consumption is way to much can you source another pump. I had this happen to me once a mate following Mr had oil on his visor! I just replaced the pump and it solved the problem.........
I agree, that does sound outrageous but 10 mm drop marked at the upper, wider part of that plastic tank or at the lower much narrower part of the tank and I also tried swapping out a spare oil pump years back and it did cure an excessive smoke problem for me also. Right now, my T500 does seem to be smoking a little more than it should. I'm going to address the carbs and probably the oil pump discharge rate test below.


CFS wrote:
I also drained the crankcases through the drain bolts at the base of the crank and minimal oil came out.................I checked the oil reservoir and found that for the amount of mileage I done (30km) the level had dropped by approximately 10mm which I feel may be excessive. The pump doesn't leak nor do the oil lines/check valves and was set as per the manual.............................Any further advice as to what the cause may be for the excessive smoke and black oil being spat out of the exhausts is greatly welcome.
What kind of oil came out of the crank chamber and how much?
Let's hope it is only your pump but are you 100% sure there is not a slow leak from a hairline crack in the tank that caused your marked oil level drop. It's also possible because of vibration and sloshing, it could leak a little faster when you are riding the bike and you might not notice it.

Pic from an ebay listing
Image

Anyway,that would be great if it was just the pump causing the problem. Tuning in/troubleshooting for any off stock carb and exhaust modifications, I would have to leave to others and in case you missed the pump discharge rate test I posted recently, here it is again. http://www.ozebook.com/compendium/techb ... 010-14.pdf" onclick="window.open(this.href);return false;"
On your set up, you could just use a syringe. That is, hanging the barrel of an appropriately sized and marked plastic disposable dispensing syringe (larger than you actually need) connected to your supply line (bleed out any air)from the tank in place of the oil gauge from Suzuki.

Image
I might do a bit of this testing on a pump or two of my own this weekend.

Here's hoping you find the solutions soon.

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GONE.......WITH A PUFF OF SMOKE AND A BLUR OF SPOKE


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PostPosted: Sat Jun 16, 2018 12:46 pm 
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Around the block

Joined: Tue Nov 07, 2017 3:25 pm
Posts: 51
Country: Portugal
Suzuki 2-Strokes: GP125, GT380
I have a spare pump & when next home time permitting will try it out.
The marking was made at the upper limit of the reservoir. I assume the reservoir is not cracked as there is no evidence of any oil on the floor whilst the bike is parked up or any evidence of any oil leak after a ride. Everything around the reservoir and the oil pump/pump lines is dry.
The oil drained from the crank to me looks & smells like 2 stroke and not engine oil. The amount in my opinion would be around 1-2 ml from all 3 cylinders.
Again time permitting I will attempt to measure the pump output and post some comments.

Thanks for the help.
Carlos


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PostPosted: Tue Jul 03, 2018 11:06 pm 
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Around the block

Joined: Tue Jul 03, 2018 4:32 pm
Posts: 84
Country: Usa
Suzuki 2-Strokes: '74 GT250
Sounds like a bad crank seal to me. Is your transmission oil low or contaminated with gas?
edit:just realized this is a year old...


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PostPosted: Thu Jul 05, 2018 9:00 am 
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Around the block

Joined: Tue Nov 07, 2017 3:25 pm
Posts: 51
Country: Portugal
Suzuki 2-Strokes: GP125, GT380
Hi Indy 650,
This post is not a year old. My last comment was in June this year.
The transmission oil is new, there are no leaks and it is not contaminated with fuel.
I haven’t had the opportunity to try out the other oil pump I have but will assemble all components over the summer break and report back my findings.
Carlos


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PostPosted: Fri Jul 06, 2018 8:38 am 
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Around the block

Joined: Tue Jul 03, 2018 4:32 pm
Posts: 84
Country: Usa
Suzuki 2-Strokes: '74 GT250
Ya sorry I think I looked at your join date rather than the post date, sorry about that.


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