cylinders

[K6jet]

Having trouble getting a ski to run correctly (93 VXR PRO 700cc), it bogs after 1/4 throttle. Im concerned about its temperature. When on the hose and idling, the cylinder towards the stern is cool, probably 120 degrees, plenty enough for you to touch, while the forward cylinder is like 180 degrees, which scares me a bit is this normal? I think its the thermal sensor limiting the ski, but if it was it would limit at a certain RPM correct?

The ski on land bogs at 1/4 to 1/2 throttle, and when on full throttle, the RPM's hit 7 grand (not sure if its an electrical failure causing the tach to read wrong), and it bogs tremendously, also misfiring. I cut the thermal sensor off and tried keeping the wires not touching and touching and it made no difference in the bogging problem. I think its electrical, because if it was the carburetor it would change performance right? Could it be my CDI?

Also, this ski has no Rev Limitier that Im aware of, I tried putting it in water, and it bogged at 1/2 throttle, or 3 grand RPM

[K6jet]

Re: cylinders

this ski is confusing the hell outta me. Just checked both fuel filters (external and internal carburator) both are fine. It has good compression, 155 and 153, and is getting fuel, so it has to be something electrical.

I test the spark plugs to see for a good spark, and grounded them to unpainted bolts. One spark plug didnt spark at all, and that was the really hot cylinder, which makes no sense, the other one was a decent spark at best.

After itching my head as to how the hell that made any sense at all (spark plugs not firing when out of cylinder), I did a compression check (155/153) with throttle open and plugs grounded (still one not sparking)

I put the spark plugs in the cylinder, and this time to test the spark, I took a screwdriver, and inserted it into the spark boot, and made a bridge to the spark plug. I started the engine, and took away the spark, making it run on one cylinder, and then gave the spark back, and made it run on both cylinders. Noticeable difference, so now I know the spark plug is firing when inside the cylinder...

I had the spark gap close to the spark plug tip, and tried reving it up, running into my bog problem again. When revved it up, the spark got weaker and weaker, until at full throttle, there was a spark every other second or so. So, the spark isnt firing when you accelerate.

My question is what the hell is going on!!! Is it possible the CDI would do this? Also, Im thinking of a strong possibility of it being a bad ignition coil. How would I test the magneto? I know how to test the CDI, and will tomorrow. Is there anything else that could be doing this? The spark plugs are brand new by the way, so its not them... also, on observing the plugs, they are rich, because fuel isnt firing.

Please Help!:emoticond

[sadchapter]

Re: cylinders

I had some difficulties with ignition , in my case it was bad plug wires and plug caps and my charge coil was bad .

Find out what ohm resistance your'r supposed to have on wires coming from stator , charge coil is the coil that powers ignition coil , and it got very thin wires in the coil.

The other coils are lighting coil that charges battery , and pulsar that times signal to ignition , those should be ok .

Check wires also , they could have broken wire .

[K6jet]

Re: cylinders

thanks, It couldnt be the plug wires or boots if I did my screwdriver spark test right? the spark was extremely strong at idle, and died after acceleratign

Im checking the ignition coils and stator as soon as I can

[David3aces]

Re: cylinders

Does the little line (off the head) flow water?.....7 grand is all you will get out of a 700...the missfire is it's rev limiter kicking in at 7 grand....if you have 1 plug sparking strong then there is nothing wrong with the other except perhaps the plug cap is bad or it's connection to the wire is bad...remove both plug caps and check spark again...a resistor in the cap can go bad....the big ignition coil gives spark to both plugs at the same time..if one works, the other has to work also...

[K6jet]

Re: cylinders

there are two lines coming off the head, a small garden hose-ish type hose going onto the rearward cylinder, and on the front cylinder, there is a small black hose that connects to the exhaust piece (about the diameter a little pen) which no water comes out of when hooked on the hose. Water goes into the garden hose tube to the head, or out of I dont know, but only smoke exits the black hose going to the head when hooked to the hose. I was assuming the black hose was a pressure hose, because it uses little wimpy metal springs to hold it on. Is water supposed to exit this?

Also, there IS a rev limiter on this ski? (I know 7 grand is all Ill get, 6250 is actually the most you're supposed to get, 7 grand is in the red, but I was thinking an electrical problem or corroded electrical box was throwing off the tachometer. Is there a rev limiter in the CDI that kicks after a certain RPM hits?) BTW, when in the water, it does the same thing, but since water pressure hits the impeller, it ony hits 3 grand, I also thought there was a rev limiter doing this, but it bogs and misfires in water also.

Another thing, I know the spark plug boots and wires are fine, due to my screwdriver test, but if I cant figure it out, Ill replace them as a last resort. But with no spark in one plug, I know it works when in the cylinder, because I started the engine, and removed and replaced the boots to each cylinder while started, and heard the difference, so both cylinders are firing

EDIT: found out what the black hose is for, took this quote from another thread

bleeds out any trapped air from the cylinder head....allowing the head and cylinder to fill with water...it goes from the head to the (yamaha) muffler.

[David3aces]

Re: cylinders

if little hose off cylinder head does not flow water, then the head will have trapped air inside and have hot spots...the temp sender near by could be coming on and causing the ignition system to go into limp home mode...little fitting on head gets clogged easily...and, yes it does have a rev limiter built into the ignition system....if jet pump cavitates, you will get a high speed missfire...

[K6jet]

Re: cylinders

I was thinking it was the temp senser also, but for different reasons. Its all cracked and very fragile, and the wire is very frail, so I ordered another, and temporarily cut this one off, thereby eliminating the possibility of the temp sensor being the problem, since essential it is an open circuit that activates when it closes. Also, if there is no water coming out the black tube (which there isnt, only smoke, or fine mist or whatever, its hot by the way) then there is a clog or air pocket in my coolant system? If so should I open up my head and take a peak and squirt some compressed air around in there?

[David3aces]

Re: cylinders

no, I clean out nipple with small drill bit (without removing metal).....You can remove the head and clean if you want to...