Suzuki 2 Strokes

All new check valves on a set of GT750 oil lines. Got this of eBay out of UK... over $100.00
Every one leaks like a sieve.

Not what I was hoping to hear, just received two sets for my T500's, not installed yet so I can't comment on how good they are. Anyone else have any experience yet with the check valves?

Note, I bought the whole spider from him. He put his new check valves onto the lines not me. I bought them in early Jan this year? More than $100 I think plus shipping.

I was going to take my carbs off and even the starter to put new brushes before this riding season began. I figured why not change this too and be proactive. That job is a #@#$ on a GT750

When I checked my original oil lines by hanging them there were no signs of leaking. I decided to fill the one I bought from him just to be sure and every freaking one leaked and fast. I am so glad I checked them first. Not an easy job and the rate they leaked would have drained my oil tank in a weak or two I guess. I have had originals weep but, not like these.

Bloop2
Maybe put a little rubber line on them to test first.

Lately when I find one of my OEM check valves leaks I have enough spare lines and I’ll find one that is OK, swap it out to make a good line set. For me that will be my option in the future as well.

Hi,agree about replacing starter motor brushes,not a 5 minute job on the GT750
Did mine a little while ago,hope I never have to do the job again
Cheers,
Roger

I have four of these check valves on my T500 and they are working fine after 3000+ miles.

I only bought the valves, not the lines though

I thought maybe it was the line fitting over the valves at first but, it’s clearly coming out of the valve not around the line and the valve.

My advice is to test them ahead of time and then once you are done the job. I am glad I tested. Bad enough to have lost just money then damage bike from hydraulic lock or even do that job again. Lately time is more of issues these days.

Well, I also know my original lines are don't leak and fresh O-rings from Suz under the pump: the original were flatten and hard as a rock: not a waste of my time here and didn't take too long once you have things a part.

Your mileage will vary

Both extremes. Someone else on this forum holed a piston -- determined that the aftermarket check valves weren't letting enough oil pass. These old pumps don't develop enough pressure to push much oil. If the spring in these new valves is too stiff, they may never open. Maybe they found that out and have now omitted the spring. That's what it sounds like on the set that Vintageman got.
Vintageman. just as a test, see if they leak in both directions (back toward the motor). That would be interesting to see.
The oil lines with proper working check valves and the oil pump are the heart of these old Suzuki's. I wish Suzuki would reproduce.the line sets for all us poor old slobs that are fighting them. And while they're at it, some new exhausts would sell like hot cakes. When all these old lines eventually fail, our bikes are dead in the water. And worse than that -- worthless.

Here's an idea. A simple electric open/close valve between the resiviour and the pump. Key on, valve opens. Key off, valve closes

One did run backwards immediately,... the others seam to hold but, I did not test that way for more than a few seconds.

I'll think check valves needs to be on each line and they work at a fast rate. If not there air gets sucked in a line when a piston goes up. Had that issue and maybe why air always in that line. Changed check valve and no more air. Not positive but, must be why there in not one check valve even when a single feed line splits into 2 like the twins (T500, GT350, T350, etc)

Coyote wrote:Both extremes. Someone else on this forum holed a piston -- determined that the aftermarket check valves weren't letting enough oil pass.

Do you have a quote for this?

On a GT750 there are 6 check valves one each for crank feed and piston feed on all three cylinders. They are a one way ball valve with very light spring set to crack open at 2-3psi.

As a piston rises, it will create a low pressure on the valve and that might cause it to open, but on the way back down the pressure from the primary compression will tend to cause the ball valve to close - unless oil pressure is greater than crankcase pressure.

Air cannot be drawn into the oil system by a rising piston.

Just so we all know, how are people getting the old check valves off the oil octopus and getting new ones in and sealed? That's the mystery for me. If I can remove the check valves, they are easy to split and clean and check and replace if necessary.

On a gt750 the far left one is not a check valve: only five of the six are and not sure why. Both his set and mine are that way

TZ are you saying you actually repair the check valves? if just dirty for example (bet most are). So far I just test them for leak and swap out. Another test I do (bit gross) is suck on it, takes little effort (no jokes please) and it will flutter/vibrate once it cracks opens. If it does not and just open it seems to be bad I have found.

On the twins, if check valve does not hold you get air. Its a different problem then having the bike set for a long while and oil dripping into crankcase and smokes at start up(did not have that problem in this case). If you fill the line and run the engine up in rpms very soon it has air in the line only up to where it splits from 1 to 2 if I recall.

I made attempts to fix by new crush washers etc…. still came back very quickly.

I changed that one check valve, same line and no problem since. I am not 100% sure why air, but that bad check valve resulted in air in that line. It was the line feeding the mag side bearing on GT250A… that bearing had signs of no oil (discolored and polished wear line on the balls like a train wheel riding on rail over and over). I think it virtually was being starved of oil.

These things are critical now aren't they

The valves can be opened up and if the problem is the ball inside the spring trick (compressed air problem) that can be rectified. Sometimes a spring is damaged and can be replaced with one form a valve with a bad pitting issue. I'll see if I can dig up pictures of that.

Opening them up is easy. I just have now luck removing them without damaging the lines. Do you just soften them in hot water or is there a chemical dip that helps to soften them up?


ALL 6 lines have check valves.... I know what you are thinking, but go back and check (pardon the pun) that one line with a valveless banjo and you will find a check valve mid line.

The left line on a GT750 has an in-line check valve because there is not room for a line-end valve due to lack of start motor to case clearance. You couldn't make it up. I'd have enjoyed being at that technical meeting where, white-faced, the assembly engineer lambasted the design engineers for not, you know, having a chat
How do you shout 'any fool can tighten a nut with a pencil', in Japanese, while remaining courteous?

The aircooled bikes are all line-end valves.

TZ: I have heard that heat is the way to loosen off the valve to plastic, once the collar is pushed out of the way, but having attempted it myself, I have instead used the line splice method to replace the odd defective valve.

Cheers,
Mike

tz375 wrote:Just so we all know, how are people getting the old check valves off the oil octopus and getting new ones in and sealed? That's the mystery for me. If I can remove the check valves, they are easy to split and clean and check and replace if necessary.

Richard - I posted a link to the instructions a while ago, but here it is again. It works as a method, but would be difficult to do on a repeatable basis (I know there are some who disagree). Once apart, the check valve balls usually look perfect, but leak anyway. One option is to use the same trick as owners of older British bikes use with their oil pumps, which is to 'seat' the ball in the cup using a punch and by doing so refreshing the face of the seating area.I have had limited success with this personally, but a more skilled person may have better luck. I continue to use the splice method (link is here) and have had good success.

What is really needed are new OEM fittings.

I have an octopus which has one line broken off at the pump and I cannot work out a reasonable way to splice it, so it's going to supply spare check valves - or I'll get replacements.

The lines on my bike are all OK but if I leave it long enough, the crankcases very slowly fill with oil. Good for keeping seals moist but makes for smokey starts after a long hibernation.