GT750 OIL INJECTION LINES, IM NEW TO THE FORUM

[Eddie]

HI , MY NAME IS EDDIE I JUST JOINED THE FORUM AND I NEED HELP WITH A FEW QUESTIONS IF ANYBODY CAN HELP? I HAVE A 1974 GT750, ITS MY FIRST GT750 I HAVE RIDDEN THEM BEFORE BUT NEVER OWNED ONE. I BOUGHT THE BIKE ABOUT THREE YEARS AGO AND HAVE BASICALLY HAD TO REDO EVERYTHING THE PRIOR OWNER DID TO IT! IN THREE YEARS I HAVE RIDDEN THE BIKE MAYBE 70 MILES. I RECENTLY GOT HER RUNNING AGAIN AND I KEPT NOTICING THAT THE FAR RIGHT CYCLINDER WAS NOT SMOKING, I DID A CHECK AND THE PLUG LOOKED LIKE IT WAS NOT GETTING OIL, TO MAKE A LONG STORY SHORT I THINK MY OIL INJECTION LINES WERE CLOGGED. I HAVE HAD DIFFERENT PEOPLE TELL ME THE WAY TO CHECK THEM IS TO SEE IF YOU CAN "SUCK" THROUGH THEM, I DO NOT KNOW IF THIS IS RIGHT? I HAVE ABOUT 5 SETS OF LINES NOW AND I HAVE TRIED EVERYTHING TO CLEAN THEM, HOW DO YOU GUYS CLEAN THEM? I LOVE THE BIKE BUT THIS IS JUST A STUPID DESIGN, SORRY ITS FRUSTRATING, THE GUY I BOUGHT THE BIKE FROM APPARENTLY NEVER CHECKED HIS OIL TANK OR CLEANED IT AND THE FAR RIGHT CYCL., NOT THE CRANK, HAS NOT BEEN GETTING OIL FOR A LONG TIME!!! THE PISTON LOOKS PRETTY BAD IM JUST WAITING FOR IT TO SIEZE BUT IT KEEPS RUNNING! I DID A COMPRESSION CHECK AND ALL CYL. ARE 105PSI AND THE RIGHT CYCL, WITH NO OIL IS 110 PSI, WHAT IS NORMAL COMPRESSION FOR THESE? I DODNT WANT TO WRIGHT A NOVEL BUT I HAVE DONE ALOT TO THIS BIKE SO FAR AND HOPEFULLY IF I FIX THE LINES I CAN RIDE IT UNTILL THE RIGHT CYCL. GIVES UP, ILL TRY TO POST A PIC, I HAVE RESTORED OTHER BIKES, I HAVE A 1963CBM72 HONDA HAWK, A 1970 R5, AND THIS IS THE 1ST GT750, I LOVE THE BIKE BUT WHAT A POORLY DESIGNED INJECTION SYSTEM!

[Eddie]

OK, I READ THAT YOU ARE NOT SUPPOSE TO USE COMPRESSED AIR, I HAVE TO ADMITT I DID, I PROBLY REUINED SOME LINES, MY BIG QUESTION IS, HOW DO YOU KNOW IF THE CHECK VALVE IS ALLOWING THE RIGHT AMOUNT OF OIL IN? I READ THAT THEY ARE NOT SUPPOSE TO LEAK, BUT HOW DO YOU KNOW THEY ARE LETTING ENOUGH OIL IN? AND WHAT IS ENOUGH OIL? SORRY FOR THE REDUNDANT POST I HAVE READ ALOT OF THE POSTS ON HERE, AND THEY ARE ALL VERY HELPFUL , IM JUST WONDERING IF MY LINES ARE OK WHY DOES IT SEEM LIKE THE RIGHT CYL. IS GETTING NO OIL? CAN THE PUMP ONLY BE PUMPING OIL TO ONE SIDE? I THOUGHT IT PUMPS OIL IN EVERY ORIFICE AT THE SAME TIME? I HAD THE BIKE RUNNING AND THE BANJO BOLT OFF AND HAD THE OIL PUMP LEVER ALL THE WAY FORWARD AND NO OIL WAS COMING OUT? I HAD THE BIKE AT 2,000 RPM AND NOTHING, IT HAD ONE LITTLE DROP COME OUT AND THAT WAS IT, I HAD THE BIKE RUNNING AT 2 GRAN FOR A WHILE WITH THE PUMP LEVER ALL THE WAY OVER, IS THIS NORMAL?

[Scorch]

Nice looking bike, Eddie.

One of the elder Suzuki experts will be along to answer your questions, I'm sure.

[oldjapanesebikes]

Others will no doubt chime in but as a start:

- modern injector oils don't cause a lot of smoke - actually, if set up right and the engine is fully warmed up you likely won't see any smoke
- the oil injector pump is a positive displacement pump - if the inlet is good, and its bled, then it will pump
- the check valves don't let oil in - they prevent combustion gas from backing into the oil lines, and stop injector oil from draining into the engine - if they are working properly, then when the bike is in storage for a few months, no injector oil will run into the engine
- a test of whether the pump is working it to manually hold the pump arm wide open when the engine is idling (and fully warmed up) - you should get lots of smoke
- doing the same test, you should also be able to see any air bubbles in the injector lines moving forwards (if there are any)
- which banjo bolt are you referring to ? If its the inlet to the oil injector pump then take a look at service bulletin # GT-2 which can be found at this link:

http://www.oldjapanesebikes.com/mraxl_G ... etins.html" onclick="window.open(this.href);return false;

- also consider opening up the oil line opening a bit on the swing arm side of the injector pump cover to ensure there is no chance of the line being pinched.
- open the bleed screw and ensure you have a good flow of oil through the pump - if you do, then normally you should be OK - there are instances where a port on the pump is stuck - normally I'd refer you to the pinkpossum.com web site, but it appears to be off line at the moment so take a look at this link for how the pump works, and possible pump problems:

http://www.oldjapanesebikes.com/fieldgu ... lpump.html" onclick="window.open(this.href);return false;"

Hope that helps !!
PS: you can take the caps lock off so you don't appear to be shouting !!

[Eddie]

Hi, thanks for the reply, I read the article on the pumps and maybe thats what happened to mine, it seems as though all the lines are getting oil except the two lines (crank and cyl.) on the right side of the bike. I think that either one of the pistons might be stuck in the pump or the check valves are not letting oil through, it says it is possible for the check valves to be stuck. I have taken them off a couple of times and sprayed carb cleaner through them, i soaked them, and a guy who is suppose to be an expert on these told me to blow compressed air threw them, and then I saw this site and everybody says not to do that, and i see why, I had no idea what the inside of the oil injection lines looked like, the banjos, and now i see why you should not use air! then another guy told me that you should be able to suck through the lines and if not they are clogged? so far i have got more info from this site than anywhere, THANK YOU GUYS!!! im just worried about the right cyl. I have no idea how long the previous owner rode it without it getting oil! I think he found the bike and just got it running but never actually cleaned anything, like the oil tank, when i cleaned it it was full of crap!!! so far I have gone through 5 gas tanks trying to find a good one, i finally found one that I could use, I rechromed the fenders and fork ears, it has new paint, i put all balls tappered bearings in the front(steering) it has new brake calipers, pads, and shoes, I rebuilt the carbs, it has a new petcock, and chain and swingarm bushings, I thought everything was good untill I started ridding and checking the plugs, and like i said the right cyl. was not getting any oil as far as i can tell, i even took the header pipes off and carbs off, and looked in the cyl. and the far right piston was dry with no oil, and the cyl. looked like maybe it had seized at one time, not sure, but it looked pretty scared up, and piston looked bad compared to the others, i hope i can fix the oil prob, and it will be ok for a while?

[Eddie]

this is the 1963 cbm72, just thought you guys might like to see it, i know this is a suzuki sight please dont hate me, but i love this bike, its not a u.s. model it is a type 2 it has a 360 degree crank with twin carbs and one set of points., the U.S. models had 180 degree cranks with two set of points and two carbs,, i restored it about 15 years ago, sorry but this is the only pic i have of it on my comp. well im not sure i can upload the pic? sorry if it doesnt ill try later.. well i cant seem to get it? it says extension not allowed? I suck at computers....

[tz375]

Eddie,
Everyone needs a CB72/77 in their stable at some time. They are cool bikes.

The oil line dilemna has to be fixed and it's not too hard to do.

Oil Pump:
The pump has two plungers, a long one for the cylinders and short one for the big ends, so if it pumps to one, it will pump to the others - as long as an orifice is not clogged and that it rare but possible.

Lines
Check valves have small balls on springs that close the line to compression pressure but allow oil to flow at around 2-3PSI they crack open. Valves are often clogged and prevent oil flow and at other times they fail in the OPEN position

Nozzles/Jets
Inside the intake ports are short brass jets which are pressed in from below and are designed to allow the oil to discharge in the middle of the air stream. That isn't strictly necessary, but they do need to be clean and it's something that is rarely checked because they rarely cause a problem. They are a simple tube with a tiny orifice (jet) at the tip.

Checking
The simple way to check is to remove the carbs ( I know ) and pump cover and pinch the oil line off. Remove the pump and set it aside. Use a small oil can with fresh oil - preferably a different color to the oil in the tank - and pump it through all the lines. You need to leave the rubber O rings in place to seal the oil can against the Octopus and you should have to pump slightly before the oil goes through.

If one of the check valves or oil jets are blocked, it may be difficult or impossible to force oil through that line. If so, remove the octopus and clean it. With the Octopus removed, you should be able to force oil through the suspect hole that the banjo bolt goes in.

Pump check.
You can check the oil pump output on a jig like Ian designed, or simply unpinch the line and rotate the pump shaft a couple of times and you should see a small amount of oil issue from each of the ports on the lower face of the pump. If only some of the ports emit oil, the pump may be faulty and may need to be repaired or replaced.

Line cleaning
I tried pumping Rubbing alcohol through but oil isn't very soluble in that and after running a bottle of the stuff through I changed plans. I shot carb cleaner down the lines followed by a WD40 rinse. Then I used the oil can to pump all six lines full of oil and then I hung it up and left it for 24 hours. The oil should not have leaked out of the check valves during that time.

Assembly
Replace the parts and fill all the oil lines with contrasting color oil. It can be almost any oil including 4 stroke oil for that.
Replace the pump and loosen the bleed screw until oil starts to bleed out then pinch it closed. Run the bike and check that the oil in the lines changes color in all 6 lines. Big ends change more slowly than cylinders of course.

Hope that helps

[Eddie]

Thanks alot, i appreciate the info, but in order to run the bike and see all the lines i guess you have to leave the chrome cover off? the cover that covers the lines? and in order to take that off you have to drain radiator fluid? this is the way I have done it but if theres an easier way im all ears! also what is the recommended compression? all of mine are 105psi and the right one is 110, is this ok compression? im afraid im going to have to redo the top end at least pretty soon, so i figure i should do the crank while im in there? what a pain in the @##$, i would hate to have the motor out and do the top end, and then put it all together and find out the crank seals are bad,,,,thats the kind of luck i have,,, I have new pistons for it, but i need to make the metal plate to pull the head off, and i would have to send theh crank out, not sure who you guys recommen? hopefully i can fix oil problem and the bike will run like that for a long time? but knowing that the right cyl. looks crapy it would bother the thell out of me..

[Eddie]

ONCE AGAIN THANKS TO EVERYBODY FOR YOUR HELP, IF I CANT FIGURE SOMETHING OUT I WILL POST AGAIN,, THANKS AGAIN, I KNOW THIS SUBJECT HAS PROBLY BEEN COVERED ALREADY, SORRY IF I BROUGHT IT ALL BACK UP, I UNDERSTAND WHY NOT TO CLEAN THE LINES WITH AIR!!! ALSO IM GOING TO BE RUNNING SI-7 FOR 2 STROKE OIL IF THE BIKE DOESNT SEIZE ANYTIME SOON, I HEARD THIS IS GOOD STUFF BUT IV NEVER USED IT, ILL RE-POST WHEN IM DONE OR WHILE WORKING ON IT,, ....

[oldjapanesebikes]

To pull the whole injector line set off to do a full clean and test you would indeed need to pull the starter motor cover off - which does mean draining the radiator, pull the starter motor, carbs off etc. - not a 5 minute job by any means. However, much of Richard has offered can be done with just the oil pump cover removed. As he says, with the pump off just use an oil can to manually fill each line under the pump - that will tell you that each line is clear. And if as he suggests, you use a different colour of oil than in the injector tank then you will easily be able to see the oil moving in the lines with the pump re-installed, the pump cover still off and the engine idling with the pump arm pulled back at max. pump rate.

Re compression - a new engine typically has about 120 psi across the board, and I've seen tired old engines running happily with mid-80's psi, so your readings are fine.

[Eddie]

YUP THATS WHAT I THOUGHT, THIS WILL BE MY 3RD TIME DOING IT! WELL ITS GOING TO BE A WHILE BEFORE I DO IT, I HAVE TO FIND A GOOD SET OF LINES, THE ONES ON THERE RIGHT NOW ARE NOT GOOD, THE CHECK VALVES LEAK, PROBLY BECUASE I CLEANED THEM WITH AIR,,,,@##$%%$ OHH WELL LIVE AND LEARN, I HAVE PRIMMED THE LINES BEFORE AND RAN CARB CLEANER THROUGH THEM, I USED AIR BECAUSE ONE LINE WAS CLOGGED AND I TRIED EVERYTHING AND I COULD NOT UNCLOGG IT, THEN A GUY TOLD ME TO TRY AIR, JUST NOT TO MUCH AND I GUESS NOW SEEING WHAT THEY LOOK LIKE INSIDE, VERY LITTLE AIR WOULD SCREW THESE UP! AND IM PRETTY SURE THATS WHAT HAPPENED, THE BIKE SMOKES LIKE CRAZY NOW AND IT NEVER USED TO, SO I NEED TO FIND SOME LINES FIRST NO USE IN TAKING IT ALL APART UNTILL I DO THAT 1ST,,,,,THANKS!!