Guys, I had a decent success today getting my 97 GTI back in the water. I had the 80g spring in my carb at 36psi pop off and mixtures at factory 1.75 LSN. And 0 HSN. Factory jets at 175/67.5. Out of the hole and midrange seemed good. But on wot it was sputtering but couldn’t tell if it was lean or rich. Plug chop was inconclusive since they had about 30 mins on them from before. I swapped in a lighter spring that yielded 26psi pop off, the top end cleaned up and felt really strong. So I put my last set of new plugs in and ride about 5 mins and did a wot plug chop. The plug to me seems lean. Was that not enough time? Could a lighter pop off make it lean? I’ll attach a pic of the plug.
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Pop off lean 717?
- Thread starter Spraddad5
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Carbs should be rich at that pop-off setting. I find most carbs to better at the upper end of the set up range. How is the ski idling? Is it hanging or dropping down to idle with no issues. How does it accelerate after a period of idling?
I'd try to rule out an intake leak or crank seal.. Good Luck !
I'd try to rule out an intake leak or crank seal.. Good Luck !
It idles around perfect. Maybe a tiny bit of that common bog just of idle after cooling off a bit. But it gets up on plane quick and seems to be good after a long idle as well. Any ideas on how to check for crank seals? The top end is new I put that in, but I bought it used so the bottom end o have no idea of hours. Just know it’s an sbt based on the crank welds I saw.
Crank seals were just a thought if you're lean. Not an easy check and I'd check that last. I'm just surprised you are so far down on the Pop-Off range. Not saying that is a bad thing. Did you check your main jet size? What's funny is, and it bit me once, the1996 GTI Pop-Off range is 36-60. I sure can't figure that one out.
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You have something wrong with your ski.
You are running lean for same reason and you messing with the pop-off spring and jetting is just masking the problem.
Stop messing with the pop-off springs and jetting and find the cause of it running lean. You should be running stock carb settings and springs and be perfect on the jetting.
You are running lean for same reason and you messing with the pop-off spring and jetting is just masking the problem.
Stop messing with the pop-off springs and jetting and find the cause of it running lean. You should be running stock carb settings and springs and be perfect on the jetting.
Yes miki I agree I have something wrong with my ski. That’s why I’m here asking for help. I’m learning. As you did I’m sure. They make different jets and springs for a reason I’d assume. This ski is not new and not at stock bore. It’s 1mm over. I’m chasing an issue I can’t put my finger on. I bought it used with a brand new, never used mikuni bin-40i with the accelerator pump bolted on. Ran like crap but wasn’t lean. Put the original non pump carb on at factory specs and pop and the plug seemed “sooty” and it was was not steady rpms at wot. Opened the HSN up 2-3 turns slowly and it seemed the same and midrange started to get lazy. Put the 26psi pop spring in, the midrange came back, top end felt good and strong, but plug chop showed lean. I’m going back to factory 36psi pop and trying again. The way I see it, I have no choice but to “mess” with it to trouble shoot. Is there another way when everything else seems ok?
1997 GTI with stock carb should run perfect at..
175 Main, 67.5 Pilot
1.5 needle and seat and 80 gram spring,
High 1-1/2, Low 1.
IF you are using the accelerator pump carb...
167.5 main, 75 pilot
2.0 needle and seat, 115 gram spring
low 1, High 0.
Oversized pistons will not cause any change in carbs.
If you are lean it is from an air leak in the engine or in the fuel supply. Typically the fuel shutoff valve or the fuel strainer.
175 Main, 67.5 Pilot
1.5 needle and seat and 80 gram spring,
High 1-1/2, Low 1.
IF you are using the accelerator pump carb...
167.5 main, 75 pilot
2.0 needle and seat, 115 gram spring
low 1, High 0.
Oversized pistons will not cause any change in carbs.
If you are lean it is from an air leak in the engine or in the fuel supply. Typically the fuel shutoff valve or the fuel strainer.
Ok thank you that’s good info. My 1997 service manual has me at 1 3/4 on the LSN and 0 on the HSN on the non pumper carb. So I’ll start fresh with that. And the pumper carb I have had a 1.5 needle/seat. And that carb wasn’t factory on a GTI until 1998 so I’ve been looking for factory specs for mixture screws.
To be clear, you can absolutely reuse the intake gaskets if they're in good shape. But if one is nicked or torn, even a little bit, consider replacing it.
If you're having the same problem in both cylinders, this is not likely your problem.
It’s a single carb ski so it could be an issue. You guys ever replace the thin seal that goes around the rotary valve cover? I ordered one from sbt and it was way too thick. The original looked like a square edged oring. One from sbt was a traditional round oring but was too thick to allow the cover to bolt up tight. So I had to reuse the old seal. Maybe that’s the problem but I don’t know where to get an OEM cover seal.
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