Thread: Big carb bogging issue GP1200R
07-02-2011, 11:10 PM #1
Big carb bogging issue GP1200R
So I have noticed my GPR has a bogging problem. It is fine when it's cool and low humidity, even hotter temps (mid 80s). But today it was 90 degrees and very humid. And it runs like a three legged dog! That and it bogs so bad, I have to coax it along for a few minutes before it finally opens up....My Dad says the carbs need cleaned and rejetted (which is a huge task given the carb location)..Should I back off on the 40:1 I am running? The engine is stock, all my mods are hull-related. Running Chevron Techron additive seems to help his ski, as it does a few others' skis...But me thinks the carbs need a good re-work. But I have put in the Chevron additive too, and while it helps it's not a cure all....I am thinking it's the low speed jets since once it "clears its throat" it runs fine...
Just an example...ran the ski last week early morning at 58 degrees and low humidity (cold!) and the dreamometer pegged at 75 (I know it's not true, I've GPS'd it at 65+)...Later in the week when it got more humid and hot (80+) the dream-o would barely touch 72...without the GPS I know what it's running b/c while the speedo is off by MPH it is accurate in terms of relative speed....
Any help here would be nice!
07-03-2011, 11:17 AM #2
- Join Date
- Jan 2006
- Texas City, Texas
If you think that it is your carbs, then if you apply about 3/8 choke, you basicly create enough vacume for the low speed to get more fuel during hole shot and your boat should run better on the bottom end (but run poorly on the top). It is a quick test.
07-05-2011, 07:04 PM #3
- Join Date
- Jun 2008
- Hillsborough, North Carolina
How many hours on this ski? What mods have been done? Is there a D-plate installed or is it stock cat con? At first glance I'd suspect the power valves. Have you inspected/cleaned up the power valves recently? Have you tested the power valves/controller?
Although it doesn't sound like a compression problem but have you tested the compression of all cylinders yet?
Keep us updated and we'll keep trying to help!
07-05-2011, 10:49 PM #4
I did notice something when shutting off the motor just recently. Normally, after shutting off the engine, after a second or so you can hear the powervalves shut...hard to explain but it's 2 "wah wah" noises. Well this past weekend I noticed a stutter in them like "wah...wahwah"...like one of them is sticking or something. Maybe that has something to do with it.
And here's another interesting thing. When we bought the ski, put about half a tank of 93 octane gas and I went out for a ride. It wasn't too long before I realized something was wrong....I know engine seizures from running lean on oil, from my years of riding, and mine began to seize...I shut it off and swam it in (we were close to the dock). After pouring in a ton of oil into the gas tank it started right up and was fine. Keep in mind this was right after we bought it and before we had the chance to get into the engine compartment....Long story short, the oil tank in my GPR is still full as the day we bought it (ought to strangle the idiots that sold it to us for not mentioning the oil pump was out/bad)...but maybe some of that oil is being somehow weakly pumped into the engine? I guess I need to check the oil tank level next time out....
Why we didn't just block it off? Well I wanted it on the water (it was Indiana summer, not that long), and Dad said premix at 50:1 wouldn't hurt in case the pump was working, worst result is fouled plugs and smoking...
Oh, and after that whole situation I got my fastest acceleration and top speed readings, so it must not have affected the engine as far as performance goes.
But here's where I am at...It still hits 65+ MPH on the GPS in cool conditions, as in my sig it hit 67 for a bit in perfect air/humidity conditions (72 degrees, very low humidity, near glass water)
I pretty much know the carbs are the issue, and I will live with that until I can break the motor apart...besides since my dad has a kick ass 1390 I want to beat him (he set it up for holeshot to beat the newer Doo's and other supercharged PWCs, hasn't been beat so far on our lake)
07-06-2011, 08:17 AM #5
- Join Date
- Aug 2006
I agree with your super DAD, clean those carbs. Whats a little work gaining access if it gets you a better running GPR? BTW, if you reduce the oil you put in the premix, IE: go from 40-1 to 50-1, you will actually richen up the mixture(fuel wise) because for a given jet size, the less oil in the mix, the more fuel is in the mix and thus the richer it is.
PS, can I borrow your GPS, cause I just might have an 80 mph GPR after all! ~
Last edited by LT1GMC; 07-06-2011 at 08:21 AM. Reason: Additional info.
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