Thread: 1100cc questions
04-03-2007, 10:33 PM #1
I'm old school now
Are the 1100 and 1200 cc cylinders the same (port wise) except for bore size?
Are the 1100 and 1200cc cases the same?
Timing curves the same?
I'm building a new project boat and have a nice 1100cc motor but if it cant be massaged to pull the power of a 1200 i need to know before i drop any money into it. I plan on running 44's instead of the 38's, milling the head, matching up the castings to the sleeves.
Most of my wrench experience is with the 701 motor which is almost idential to 2/3 of the 1100 motor so I plan on using a similar setup that i've run for years on the 701. However I know this board is rich in knowledge on these motors and would listen to any advice on setup
04-03-2007, 10:42 PM #2
I'm pretty sure you're right about the cylinders and ports. Only the bore is different. The 1200 cylinders that i have seen all have 63m casting marks.
Timing is different. 1100 has 1 curve, 1200 has 1 for each cylinder. parts will swap over. just need a 1200 flywheel and cdi. the 1100 ebox can be used. look for a post on it by oldmanraider.
Carbs, reeds and intake are different, but are a direct swap except for pulse lines.
The cases are the same except the 1200 has 3 pulse lines and the 1100 has 1. the cranks are the same except for the front bearing, and I think 1 locating pin in the case.
You're right about the 1100 being basically a 701 with and extra cylinder. Great motors. Just realize that "high" compression on a tripple is alot less than on a twin. 150 is usually the pump gas limit.
04-03-2007, 10:58 PM #3
The difference in the case is the 1200 has two extra pulse fittings for the three fuel pumps on the 44 sbn carbs that come with the 1200 as compared to the single pump on the 1100. It's not hard to add these if you want to run the 44's, that's what I did.
I'm not sure about the port size but I think the 1200 ports might be a little larger. The ports can be enlarged on the 1100 cylinder though. The 1100 cylinder can be bored up to a 1200.
The timing is different for the 1200. It has a different curve for each cylinder which helps the engine to run cooler. You can change to a 1200 cdi and flywheel with out much trouble. One of the plugs on the cdi needs to be swaped from the 1100 cdi but the wire colors are the same and it only takes a few minutes to change the plug.
The reeds and cages are longer on the 1200 verse the 1100 but can be found on ebay for cheap.
Hope this helps
04-04-2007, 06:06 AM #4
Those two have covered just about everything....the 1200 has different porting specs than the 1100, but as you said you can trim them up to match .also the 1100 can be bored to 1200 ..84.oo mm and still bore it to 84.25, then 84.50 after that
04-04-2007, 08:18 AM #5
Is it possible that the ports are different only because the bore is larger? If they start out the same when the sleeve is installed, then you bore 1 larger than the other, wouldn't that make the larger one have larger ports?
Educate me please!
04-04-2007, 08:41 AM #6
There is a 701 and 760 yamaha twin cylinder the 701 has the 81mm pistons and the 760 has 84mm pistons. The two have different port timings, a 701 opened up to the bore size of the 760 doesn't run the same as the 701, Ive alway found the 701 (61x version ) to have better low end power.
I didn't know if the 1100 and 1200 cylinders were similar in this respect.
04-04-2007, 08:44 AM #7
Mike ,I am here at work ,I dont have my notes but the timing is different like ram jet was talking about...by all means go with the 1200 or 760 reed cages, or vf'2s or now vf3's
04-04-2007, 08:45 AM #8
The 760 i think is 2/3 rds of the 1200 65U motor. The 62T 701 i believe is 2/3rds the 1100 63m motor. I don't think the 61x's really compare to the tripples.
04-04-2007, 08:47 AM #9
04-04-2007, 08:49 AM #10
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