DylanS
Gorilla Smasher
- Location
- Lebanon Pa
Are you using the bottom end from a 1100 ?
In line external mukuni DF62 fuel pump verses internal carburetor fuel pump for a GP 1200.
- Thread starter Radical Riche
- Start date
- Location
- Lower Burrell Pa 15068
I'm using a 1100 case modified to use a 1200 block. It's the same case other than modifying for the 1200 sleeves.
1100
DylanS
Gorilla Smasher
- Location
- Lebanon Pa
I'm using a 1100 case modified to use a 1200 block. It's the same case other than modifying for the 1200 sleeves.
This generates catastrophic heat and shows up as a lean condition.
Now they claim they have no solid evidence BUT I know the 96? 1100ZXI’s began to pull the ignition timing back on the rear cylinder at certain temps and rpm and I believe Yamaha did the same on the 1200 electronics. Someone who knows more history about sit downs might know better.
Anyways you’ll also see engines like the 64u that have lower rear cyl compression from factory and retard the timing of that cyl.
As far as seals blowing on 1100 cranks I never had that be much of an issue but I have fought the notorious lean rear cyl condition many a time
There’s a article group k make about crank torsion where they claim that because the rear most cyl is closest to the pump and furthest from the flywheel that it twists under heavy load and actually advances the timing 2-3 degrees on that cyl.
This generates catastrophic heat and shows up as a lean condition.
Now they claim they have no solid evidence BUT I know the 96? 1100ZXI’s began to pull the ignition timing back on the rear cylinder at certain temps and rpm and I believe Yamaha did the same on the 1200 electronics. Someone who knows more history about sit downs might know better.
Anyways you’ll also see engines like the 64u that have lower rear cyl compression from factory and retard the timing of that cyl.
As far as seals blowing on 1100 cranks I never had that be much of an issue but I have fought the notorious lean rear cyl condition many a time
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- Location
- Lower Burrell Pa 15068
How would you change the time in the rear cylinder? Thanks that was very knowledgeable!
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
No I run the three internal pumps but decrease popoff and drill the restrictors out of the carbs. A good backfire will blow the rear crank seal right out of the crankcase.
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
You can't really , Yamaha did it by changing the position of the pickup on the case.
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
Crank torsion Ing is a real issue and occurs on skis with heavy pump loading and big hulls, you would rarely if ever see it on a triple mounted in a standup or a Blaster, on something like say Yamaha SUV or an XLT 1200 it becomes a real issue because of the size and weight of the hull and the weight of the riders and whatever they packed into the massive storage buckets on these skis , three or four riders plus a massive hull equals massive pump loading , Yamaha staggered the timing, the jetting and lowered the compression on the rear cylinder because of this.
The 1100 engine was never put in anything bigger than a Waveventure hull with the exception of the Exciter jet boats, those had twin 1100.s though.
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- Location
- Lower Burrell Pa 15068
I don't run restrictors..should I? I've heard about backfires causing seal to blow out. How do you avoid a backfire though?
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
By having it jetted properly. lean conditions cause backfires, the restrictors are built into the carb bodies unless they have been drilled out, if you drill them out then you use a restrictor in the return line.
- Location
- Lower Burrell Pa 15068
No I never drilled them out so I should be good. I was running 110 pilot jet 135 main, 2.0 n/S , 95 gram spring with 25lbs pop off. I think I had a case leak causing the lean condition .
DylanS
Gorilla Smasher
- Location
- Lebanon Pa
Do you know how to perform a leak down test when you assemble your engine?
Well that changes everything. The question now is how much did they reduce the main jet signal and how consistent was the machining between all three carbs? To begin, you have three individual cylinders that have different mixture requirements. Add to that, now you have carbs that may be different in their ability to pull fuel. The problem with this is one hot cylinder will be difficult to detect without a way to measure combustion temps. All the two stroke , especially three cylinder development, ended up with concessions to keep them from burning a piston. They are usually not a problem when mounted in a standup since the pumps cannot load them very well. You need to master carb tuning on a single carb ski before moving to multi carb arrangements.
- Location
- Lower Burrell Pa 15068
Oh im good at tuning carbs that's what saved me from destroying my engine. When I had carbs on the 1100 that engine lasted over 8 years till I decided to go with a 1200 head. I'm more worried if the external fuel pump is sending wrong signal to carbs.
- Location
- Lower Burrell Pa 15068
I'm lost on the restrictors, I have mikuni 44 BN which are taper bored. I didn't drill and restrictors out of carbs nor do I have any restrictors in my return line. I have a external fuel pump with each having it's own fuel line from the mikuni DF62 fuel pump. I would have to way to monitor fuel pressure guage inside engine compartment on a B1. I'm leaning going back to internal pumps in carbs, I didn't have this problem with the 1100 which lasted 8 years. I had 150 psi compression before I discovered my lean condition. I can hone cylinder, buy new piston and rings and change to 125 pilot and 145 main. But I still think I had a case leak which caused the lean condition. There's fuel wash on top of all 3 pistons so it was dumping the fuel. Thanks for your help!!
- Location
- Lower Burrell Pa 15068
Yes but making up all the block off covers are gonna be a pain. I don't know anyone that sells them for a triple
DylanS
Gorilla Smasher
- Location
- Lebanon Pa
take a gasket and a piece of 5/16 Allum plate to a machine shop or someone with a plasma cutter and have them make you plates if you don’t feel like making them yourself.
leak down testing is a very important part of building the engine.
- Location
- Lower Burrell Pa 15068
Yes I agree. Torrent makes them for 2 cylinders, I told Brain he should make them for 3 cylinders that most B1s are triples now
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
What signal is this that you keep referring to the fuel pump sends fuel to the carbs that's its function, and signal is in the carb itself and refers to it's ability to draw fuel into the jets, vacuum is another way to put it, signal can be and I guess in this case is very misleading.
'
A pulse type pump is a bit digital in output but it smooths out at high rpms. A Blaster is easier to tune while tied to a trailer since you can sink it deeper than a standup. I can get most of the tuning work done with the ski tied down and sunk up to the hood seal. Often the peak RPM is the same as it is at full speed on glass.