Oil for a GT250k

Everything you want to know about oil but were "afraid to ask"!

Moderators: H2RICK, diamondj, Suzsmokeyallan, oldjapanesebikes

Post Reply
User avatar
Bmurphybcr
Still in the Driveway
Posts: 7
Joined: Thu Sep 02, 2021 3:31 pm
Country: United States
Suzuki 2-Strokes: 1973 GT250k
Location: Lakeland, FL

Oil for a GT250k

Post by Bmurphybcr »

I'm trying to restore my grandpa's 1973 GT250k and get it up and running again. So I'm guessing the oil reservoir on the right side is for 2 stroke oil... How much gear oil do I add and is there no motor oil for a 2 stroke? Is there not an oil filter? If there is, where is it? I have no idea. This stuff is foreign to me. I plan on running premix just incase there's a problem, but what is the ratio I should mix? My greatest fear is to get this thing to start up and seize up. Keep in mind this thing was last on the street in 1981. I'm only trying to do a light restoration, so if at all possible I'm not going to rebuild the engine or the carbs. It's only got 4,000 miles on it. I'm clueless when it comes to 2 stokes so explain it to me like I'm 8 years old please. Thanks. :up:
karl pa
To the on ramp
Posts: 390
Joined: Sat Sep 05, 2015 3:14 pm
Country: us
Suzuki 2-Strokes: GT
Location: southeast pa

Re: Oil for a GT250k

Post by karl pa »

Welcome to the forum.
Yes, the 2 stroke tank is on the right side.You should drain any remaining 2 stroke oil from the tank, The old style oil and the new style oil when mixed can clog the system.
If you check oldjapanesebikes.com Under Suzuki T/GT resources, you will find Suzuki manuals. Looking at the GT250 owners manual it shows 1300 cc for transmission. 2 stroke engines use the 2 stroke oil to lube the crankshaft and cylinders. Suzuki GT has no oil filter.
Suzuki 2 strokes use oil guides on crank that pull oil from bearings, that is why you never want to run them on only premix, it will starve the bearings of oil. I assume you want to run premix till oil system is working, I would think 50/1 would be enough, but remember it is not oiling the main bearings. There are ways to prime the oil lines.
I am afraid to say but, most likely you will need to remove carbs for a good cleaning, and setting for so long there is a good chance the crank seals will leak :(
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe
User avatar
jabcb
Moto GP
Posts: 3854
Joined: Mon Dec 13, 2010 4:32 pm
Country: USA
Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Re: Oil for a GT250k

Post by jabcb »

Welcome to the forum. You have what could be a fun project. Especially because of it's family history.

I’ve not tried it. But others have forum posts where they talk about a procedure to renew the crank seals. I think some have used diesel fuel + something else. Perhaps a forum member could post more info about it.

It has been sitting long enough for the two stroke oil to gum up the oil lines & oil pump. Likely will be fine if you drain the oil tank, rebuild the oil pump & flush out the oil lines.

Does the motor turn over easily with the spark plugs removed?

Best to review the manuals that Karl mentioned & post questions here before each task. (Everyone has busy lives, so sometimes it will take longer than you would expect for a response.)
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
User avatar
Alan H
Moto GP
Posts: 2699
Joined: Thu Feb 16, 2012 11:50 am
Country: England
Suzuki 2-Strokes: 2 x GT550s GT750B, GS750B
Location: The Republic of South Yorkshire

Re: Oil for a GT250k

Post by Alan H »

viewtopic.php?f=2&t=14715&p=177418&hilit=Diesel#p177418
There y'go. Welcome to the forum.
It's always nice to do an intro but you've covered the 'previous biking' bit! Which general bit of the world do you inhabit? There might be someone local to you that can help.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
User avatar
GTFIZZ
On the street
Posts: 19
Joined: Thu Oct 29, 2020 1:38 am
Country: Guernsey
Suzuki 2-Strokes: Gt185 1976 , Yamaha FS1e 1975

Re: Oil for a GT250k

Post by GTFIZZ »

jabcb wrote: Sat Sep 04, 2021 6:20 am Likely will be fine if you drain the oil tank, rebuild the oil pump & flush out the oil lines.
Sorry to highjack this tread, but you mention rebuilding the oil pump, any pointers to how? as I have what I think an oil pump problem(maybe in my head, but that’s another story :D ) I have 2 spare pumps(GT185) and by testing them, one pumps more oil than the other, so would be interested to see if I can get them both the same?

Again sorry to highjack
User avatar
Bmurphybcr
Still in the Driveway
Posts: 7
Joined: Thu Sep 02, 2021 3:31 pm
Country: United States
Suzuki 2-Strokes: 1973 GT250k
Location: Lakeland, FL

Re: Oil for a GT250k

Post by Bmurphybcr »

Thanks for making me feel welcomed! I appreciate the website. The shop manual will go a long way. The motor does turn over easily. Alan, when TOwenR says pull the barrels off, does he mean the cylinders? Then I just pour diesel into the crankcase kick it over a bunch of times and let it soak? To answer your question, I live in Lakeland, Florida. I used to ride an '06 Yamaha V Star I bought brand new and rode everywhere till I was forced to sell it because of bankruptcy in 2019. :cry: GTFIZZ, I was wondering how to go about it as well. I'm not even sure where the oil pump is. I guess I'll look through the manual. Is there a rebuild kit? Thanks for the info.
User avatar
jabcb
Moto GP
Posts: 3854
Joined: Mon Dec 13, 2010 4:32 pm
Country: USA
Suzuki 2-Strokes: 69 T350 thru 75 GT750
Location: southwestern Pennsylvania

Re: Oil for a GT250k

Post by jabcb »

You should start a new topic to ask about the GT185 oil pump. I have no experience what the pump, but maybe someone else does.
BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 69 project & 73 project
T350 69 & 71
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE
User avatar
Alan H
Moto GP
Posts: 2699
Joined: Thu Feb 16, 2012 11:50 am
Country: England
Suzuki 2-Strokes: 2 x GT550s GT750B, GS750B
Location: The Republic of South Yorkshire

Re: Oil for a GT250k

Post by Alan H »

Bmurphybcr wrote: Sat Sep 04, 2021 3:43 pm The motor does turn over easily. Alan, when TOwenR says pull the barrels off, does he mean the cylinders?
Yes.
Then I just pour diesel into the crankcase kick it over a bunch of times and let it soak?
No, you turn it slowly, many times and don't let anything (like con rods) bang into things. Remove the cylinder heads, pistons and piston pins - carefully - first. Read my posts on the subject - do a search for 'diesel'. (Top left of the screen on 'Quick links'. Click the 3 lines and look for search there..
To answer your question, I live in Lakeland, Florida. I used to ride an '06 Yamaha V Star I bought brand new and rode everywhere till I was forced to sell it because of bankruptcy in 2019. :cry: GTFIZZ, I was wondering how to go about it as well. I'm not even sure where the oil pump is.
Follow the pipe from the oil tank. It's on top of the engine. You didn't think all this was going to be straightforward did you? :)
Is there a rebuild kit?
Not usually needed, just care and being careful.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
karl pa
To the on ramp
Posts: 390
Joined: Sat Sep 05, 2015 3:14 pm
Country: us
Suzuki 2-Strokes: GT
Location: southeast pa

Re: Oil for a GT250k

Post by karl pa »

I use diesel fuel and Blue Devil seal repair, and fill crankcase so seals are covered,I also remove transmission drain plug, if seals are leaking, the mixture will drain out the transmission drain hole.
My 75 T500 and 71 T250 have questionable center crank seals, when I change transmission oil I add Blue Devil seal repair and seems to be working.
There is a forum member sells seal and o rings kit for T/GT250 on ebay, I just replaced my 71 T250 oil pump seals and o rings because my 2 stroke tank drained through the lower pump shaft seal and into the transmission.
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe
User avatar
GTFIZZ
On the street
Posts: 19
Joined: Thu Oct 29, 2020 1:38 am
Country: Guernsey
Suzuki 2-Strokes: Gt185 1976 , Yamaha FS1e 1975

Re: Oil for a GT250k

Post by GTFIZZ »

jabcb wrote: Sat Sep 04, 2021 3:45 pm You should start a new topic to ask about the GT185 oil pump. I have no experience what the pump, but maybe someone else does.
I will, but I was reading this and you mentioned about repairing the oil pump and thought that they all would me similar?
User avatar
Bmurphybcr
Still in the Driveway
Posts: 7
Joined: Thu Sep 02, 2021 3:31 pm
Country: United States
Suzuki 2-Strokes: 1973 GT250k
Location: Lakeland, FL

Re: Oil for a GT250k

Post by Bmurphybcr »

Are you referring to the blue devil head gasket sealer? That's all that comes up when I search for blue devil seal repair. The Phillips screw heads are rounded out on the oil line cover and oil pump housing so I guess I'll have to get a screw removal kit before continuing on with the cleaning. I took your advice and took the carbs off and they definitely needed cleaning. Just hope I cleaned them well enough. One of the pistons has some pretty deep grooves on one side. I'm guessing I'll need to have the cylinders bored and honed .5 mm and buy bigger pistons?
karl pa
To the on ramp
Posts: 390
Joined: Sat Sep 05, 2015 3:14 pm
Country: us
Suzuki 2-Strokes: GT
Location: southeast pa

Re: Oil for a GT250k

Post by karl pa »

I use Blue Devil oil stop leak, I get it at Advance Auto, It is to help soften rubber seals, (sometimes it works and sometimes it doesn't)
When cleaning carbs, you need to clean all the small passages, not just jets, I spray carb cleaner and compressed air through all passages to make sure they are open, sometimes it can be very difficult to get everything clear, and you must study them to figure out where all the passages go.
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe
User avatar
Bmurphybcr
Still in the Driveway
Posts: 7
Joined: Thu Sep 02, 2021 3:31 pm
Country: United States
Suzuki 2-Strokes: 1973 GT250k
Location: Lakeland, FL

Re: Oil for a GT250k

Post by Bmurphybcr »

I took the oil pump apart and cleaned it. I got the oil lines off, but when I try to blow through them, I can't. I read on oldjapanesebikes that the ends that attach to the crankcase have valves in them, so is this normal, or should I be able to blow through them? Any ideas on what I need to do to get them unclogged if that's what I need to do?
karl pa
To the on ramp
Posts: 390
Joined: Sat Sep 05, 2015 3:14 pm
Country: us
Suzuki 2-Strokes: GT
Location: southeast pa

Re: Oil for a GT250k

Post by karl pa »

They are check valves, they open around 4-7 pound (I think) toward engine to allow oil through, never use compressed air to blow through, it will damage them. All they are is a spring and ball in a housing. If you bolt a banjo bolt in the oil pump side of lines, you can use an oil squirt can to push oil through lines, opening check valves.
After filling oil lines, hang them overnight, engine side down to see if check valves leak,(put a pan under them) If they leak when on the engine, it can fill the crankcase to the point of hydrolock. There is a way to disassemble them, but I never did.
When lines are back on engine, you can use squirt can to push some oil through lines to get some oil to main bearings before starting.
76 GT185
77 GT250
77 GT380
76 GT500
73 GT550
73 GT750
74 GT750
71 T250 scrambler
75 T500 cafe
Post Reply