1999 GTI wont go over 30mph, need help

[ironmike4134]

History... friends ski, a shop rebuilt the carb. Had hard time starting (shop said compression issue), but once you got it running it would not idle (without feathering), but it would run to about 47mph and also shoot out of the hole. I got the ski, checked compression and found it low (pulled heads/cylindar). Redid the top end with a kit and had the cylinders machined. While in there I replaced all the old gray fuel lines... took to the lake, starts like a charm, idles now, but the engine seems to "surge" when holding the throttle at a set spot... but the big problem is that if you run at WOT, it bogs down (almost dies) (pulling choke kills it immediately). If you stay at 2/3rds throttle it runs all day at 30... anything over and it bogs. It also does not shoot out of the hole like it used to with low compression.

Checked compression (good in both cylinders now)
Replaced needle and seat in carb (was not done on the rebuild) <-- helped with idle but did not help with bogging problem.
blew air through gas selector, there does not appear to be obstructions.
carb adjusted to all standard settings.
I pulled the carb and checked the rotarty valve clearance (right at limit .035). Timing looked about right (did not actually check with a guage), but no backfire/other issues.
when I pull the plugs, they are black, so think I am running rich (why I replaced the needle and seat).
put a multimeter on the battery to check to see if I might have a regulator problem (no change between engine off and engine running).
I set the oil pump at the proper check mark (but found the cable came off during the ride at some point... could this be my problem? was thinking no as it should just be over pumping oil at low speeds).
The temp guage on top of the head broke off, so it is no longer connected, is there any electronic control to limit the motor if there is no temp sensor?

Only thing I can think of now is that maybe something from the old fuel lines got into the carb (between pulling off the top-end and going to the lake?). I think the next step is to rebuild the carb again? Or could it be something I did when rebuilding the top-end? or replacing the fuel lines?

 

[Coastiejoe]

I would bypass the fuel selector for now. They can suck air at the shaft. Most replace them when they replace the GT Lines.

When you rebuilt the carbs, did you use an OEM kit or aftermarket?
Did you replace the Pop-Off springs? If so, if you have the original springs I'd put them back in. For some reason, replacement springs are almost always incorrect.

 

[ironmike4134]

I did not rebuild the carb... it was rebuilt before I got it. It was running at 47mph with the low compression (almost impossible to start and also difficult to keep running). I did a top-end rebuild and replaced the fuel lines... now wont go over 30 (but starts and idles with no problem).

Also since it dies when I pull the choke, I would assume I am not running lean rather running rich or not burning the fuel. If I was sucking air, then pulling the choke would improve things. I either need to rebuild the carb again (something may have gotten into it) or have an issue with oil pump, or heat sensor, or an exhaust leak, or??

 

[ironmike4134]

There appears to be an exhaust leak... had a little bit of water in the motor compartment... also when revving it out of the water I can see a puff of smoke coming from somewhere low on the Pipe... can this be the cause of my problems? P.S. also when I was rebuilding the top end one of the mounting bolts was missing (missing before I rebuilt it).

 

[Mickirig1]

Make sure the tuned pipe is sealed. Any water leak, means exhaust leak too. Exhaust gases makes it harder for the ski to get pure air. You may have to break down and buy a used or new carb. Sometimes no matter what you do the carb is done! I saved my sanity and just bought a used one. It fixed my problem!

 

[ORION '95 Speedster]

The exhaust leak is bad news, you want to fix that. You may be able to put some sealant over the broken gasket for now, so that you don't have to take stuff apart. As for the max speed, are you sure the throttle plate is all the way open when you are trying to go fast?

 

[ironmike4134]

Yes throttle plate is open... It used to go 47mph until I did the top end rebuild and replaced the fuel lines... (carb rebuilt before replacing fuel lines). It seems to be running rich now (pull choke and it dies). I guess the only options are to seal the exhaust leak (heard this could cause exhaust instead of air to go into the carb) and clean the carb again (in case something got in there between the top-end rebuild and the last time it ran.

 

[ORION '95 Speedster]

Your absolutely sure it sunning on both cylinders, right?

 

[ironmike4134]

Your absolutely sure it sunning on both cylinders, right?

Not sure what you are asking? the plugs in both cylinders are blackish i.e. rich.

 

[ORION '95 Speedster]

Disconnect a spark plug wire and try to start the engine. Then plug that one back in, and disconnect the other spark plug wire and try to start the engine. If the cylinder is dead, it will not run or even try to fire. Its a way to ensure that both cylinders are firing.

 

[Mickirig1]

Most of the ski's do the wasted spark system. It sends a spark voltage to both cylinders at the same time. One has a fuel charge it fires, the other is on an exhaust stroke. So no fuel charge to ignite.

 

[ORION '95 Speedster]

I agree, many types of engines have a "wasted spark". I'm not sure of the relevance.

 

[Mekanix]

This spark from this ignition system does not jump to ground.

It jumps from one spark plug to the other.

The secondary side of the coil is not connected to ground in any way. Only the two wires coming out of it are connected.

So spark goes from one wire through the plug and then uses the engine casing as a path to get to the the next spark plug and then back to the other wire.

Disconnect one wire and it just won't run.

However enough energy can jump to a large chunk of metal like the engine block but that is not the way its designed. So if you get something like that its just an anomaly or really healthy spark.

Now for running on one cylinder or not, you will get that situation if you have a fouled plug because you are still allowing the spark to go through the fouled plug and that energy goes to the good plug that does fire.

As for wasted spark. Yes. Both plugs fire at the same time every time.

Relevance none, just interesting fyi


As for what's going on, pulling the choke in this case should kill it when your onto the the main jet part of the throttle range.

The choke test has more effect in midrange and low end diagnosing but most of the time kills the engine when your on the main jet or in some way lowers performance.

I'm thinking your actually running lean. That's what the surging is telling you.

One way to eliminate only the things you've done is to do like coastie said and connect the carb directly to the reserve on the fuel sender.

I'm thinking you have an air leak somewhere in the fuel lines that you replaced. It could be right at the carb or the fuel selector or the water seperator or the water seperator gasket or the fuel sender itself is damaged from when you removed the old lines and possibly cracked one of the fittings.


After that, one more option is to use a separate test fuel tank to prove its not fuel delivery from the tank.

The next thing is like you said, maybe a chunk of crap made it to the carb filter and you'll have to tear it apart to clean it out.
Tip: use blue locktite on those screws when you put it back together.

All I can think of right now until you get some more testing and results.

 

[ORION '95 Speedster]

Umm... Your saying that the spark goes one direction though the 1st spark plug, and then back through the other spark plug in the opposite direction as the ground? I could be wrong, but I think that is not correct. The main engine ground to the battery would cause problems with that. I may be wrong. Please show me some diagrams or something, I want to learn something new.

 

[Mekanix]

I mean imagine it like a complete electrical circuit.

The secondary side of the coil isn't connected to ground at all. Its just two floating wires and the spark will only jump between these two wires.

So for experimenting and explanation you could simply connect one plug wire to the plug and the other plug wire to the body of the spark plug and lift the plug off of the engine casing so its not touching any ground. When you crank it you will get spark.

(some automotive coils that only have one output connect half of the secondary side of the coil to ground. That makes the spark jump from the output of the coil back to ground because that's where its return path is)

When you think about an automotive spark system you always test to see if the spark is jumping to the engine casing but on these machines with this coil design, its different. So pulling one plug kill's the whole circuit because there is no way for the spark to complete its circuit.

 

[ORION '95 Speedster]

Hmm. Your talking model specific, or brand specific?

 

[Mekanix]

94 on seadoo's use this coil design. Nipondenso (isolated secondary type of coil with dual output)
951's I'm not sure. I think the dual coil design on some of the 951 are like the automotive design.

I first noticed this quirk while measuring a coil that I thought was bad because there was no continuity from ground to each of the wires. Then I found it in the manual that you only measure between the wires for one measurement and then between the two inputs for the other measurements.

 

[ORION '95 Speedster]

This is an accidental discovery, as opposed to a technical diagram?

 

[ironmike4134]

Mekanix, I have clear fuel lines... I dont see any air bubbles in the line when running... I would think if I had an air leak anywhere in the fuel lines I would have bubbles right?

 

[ORION '95 Speedster]

An empty fuel line looks the same as a full fuel line.

 

[ironmike4134]

Orion, the fuel is flowing... LOL... I put it on a hose and checked the rectifer (all good)... then cranked it WOT... got a backfire through the carb at WOT... not constant, intermittent. Pulled the plugs, both are black (look good for a 2 stroke). My RV was a little worn on the gap (could force a .038 feeler through the opening in one spot). Could I be slightly out of time?

 

[Mekanix]

This is an accidental discovery, as opposed to a technical diagram?

I was helping someone that was having a no spark issue and thought the coil was bad so they showed me what they were doing and how they didn't get the right measurements they should have.
So I read the manual and found that it said only to measure between the two wires.
That's when it hit me. By design this coil is just a big step up transformer. As in the primary side and secondary side are seperate and all this thing does is boost up voltage. So looking at the wiring diagrams and reading the test procedure in the manual proved that's how its designed.
Older manual's show the inner workings of the electrical components and I've seen a few that show that's how they are made inside.
Also look at the 99 gti shop manual page 496, it shows the inside of the coil and how the primary and secondary side are separate.

Mekanix, I have clear fuel lines... I dont see any air bubbles in the line when running... I would think if I had an air leak anywhere in the fuel lines I would have bubbles right?

I would expect so. It would look almost aerated.

If the fuel source is good. (assuming there isn't a bottle neck slowing the fuel delivery at wot) The next thing is carb related.

So things to check would be
Pump diaphram for distortion or cracks
Fuel filter for cloggs. (also check that the return line orifice is clear)
Fuel needle and seat are in good shape. Ie not leaking or clogged up.
Make sure the arm isn't bent so far down below the carb body surface that its not allowing the needle valve to open up enough. Should be level with the body -+ 1mm

What are yout low speed screw and high speed screw settings ?
I wonder if the shop just unscrewed the low speed screw to make it rich and make it work with the lower compression?

LS should be within 1 -+1/4 turn of closed. And high speed closed.

RV gap would affect low speed not WOT unless its severely worn.
You notice RV problems when its hard starting.

Fuel is always flowing with this fuel system because of the return line. And its pretty quick honestly. That's how you would see the aeration in the line.

 

[ironmike4134]

I just replaced the needle/seat (before the last lake test)... fixed my idle problem. I set the low speed to 1 1/4 out (per shop manual). High speed is almost full close i.e. lean setting.. cracked open just a little. Might be getting the back fire because the plugs are a little black now... I also fixed an exhaust leak that was the rubber piece between the upper chamber and the lower exhaust... RV may be worn... but it was running 47mph before top end rebuild, and after was 30mph, so dont think it is worn to the point it is bad. Return line is flowing (I do have some air in the return line).

 

[Mekanix]

Is it just a big air bubble in the return line or is it lots of small bubbles while its running ?
It should be full and clear after the first start once its stabilized.

Possibly air is getting passed the diaphram or right at the fuel inlet.

 

[ironmike4134]

See an occassional small bubble heading back for the tank... just ran it again on WOT and really looked at the lines. The small line that comes out of the bottom of the accel pump to the top of the carb is geeting airbubbles (like an aerator at WOT). Is this normal?