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Discussion Starter · #1 ·
I thought I would start a thread about doing engine mods that are a little more complex than just buying parts and bolting things together. The bolt on stuff is the basis for modifications but there is a limit .

What got my inside my engine? I was trying to do some cam tuning with adjustable sprockets. Before I started I found I had very low compression ON #1 cylinder. I pulled the head and found the valves where leaking . I pulled the valves and found they where just not seating . I fixed that by lapping the valves and they seat now without any leakage .

But I have the engine Half torn down so I was thinking .What can I do .

I want to add pistons with Higher compression . But they have to be ordered and You have to buy 4 at a time so 500 dollars and 6-8 weeks is a winter thing

I want to do some modest head porting I don't have a flow bench . but I have some experence with this.

The other thing I was thinking was to deck the cylinder block.
The base gasket is .010 thousands thick . I took it out and checked for piston to head and piston to valve interference . It clears without a problem .

Since this is a street engine I wont do cams and carbs . So I don't want to up the compression to much .
i was think of having a machine shop mill .010 thousands of an inch off the top of the block then reassemble it with a new base and head gasket .

Any thought ?
 

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Racer X, i have not actually worked on engines like this, however I do know what you are talking about, as far as being around people that do asking questions and watching shows and that. It have always been interested in it. I just never have had the money to spend on what I want to do.
Anyways enough jabber...I'm sure that you have already checked the piston clearance for this. I was going to ask if you were going to port and polish, but I see that you are. This should produce more HP, have you got your new racing carb in yet? That should be able to give you the extra fuel needed for the increased air flow....Sorry to sound dumb, again not a mechanic, but isn't this about all that you can do to the head?
When you get new pistons are you going to bore so you can get larger pistons and crankshaft? That will be so BAD, it'll sound like a little muscle car!!
 

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this would be a great thing to learn and do down the road.. but at the momment my baby doesnt need surgery.. ;)
keep them info and pics coming X
 

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Discussion Starter · #4 ·
I have two engine projects going at once . My street engine I am doing myself . That will be just ported and polish head adjustable cam sprockets deck the head . Plus the exhaust jet kit with stock carb s and BTS ignition

For my race engine I, will have bigger carbs and I will have high compression pistons . Custom cams The head flowed on a bench by a pro. Custom springs bigger valves, Custom made roods Custom work on the oil pump and cooling system balance moving parts everything . Plus all the secret stuff
That is going slow because of the custom parts .

But I need to ride and race my bike in the mean time. So I am fixing my stock engine and trying to bump it up on my own,
 

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Racer X - The older ninjas had higher compression. If you're staying on the cheaper side, buy a new set from the dealer (cheap - $30 US each last I looked). Use a new set of rings and hone the cylinder bores.

If you have a few bucks you could go oversize (which kawi offers) and have the bores machined. Higher comp and a bit more displacement.
 

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Sounds like with the BRT ignition you'll be looking good. I just got a head back from Kibble White $1400 when it was all said and done. I'll figure out how much you can shave off of the head its not very much just can't remember the exact number. I'm looking into getting JE 12.5:1 pistons and the buying 4 at a time BS is retarded. Also your Tis will be in the mail to you on Monday. Apparently I missed DHL yesterday even though I was home either that or they just go stright to the post office now.
 

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Discussion Starter · #8 ·
I cant go oversize 250cc is the limit . I have a 350cc record . But I want a 250cc record so no over bore or stroke crank.
I got lucky with the pistons . I Split a set long a go with Generic . So that works out .
No I did not buy a wrecked ninja built I am going to .
My engine builder has at least a year back log on his schedule . Since He is the best I bought an engine from E bay in February of 2008 with only 200 miles . Since then I have bin buying parts and sending them to him . Or he has ordered the stuff I will need . But it is sitting on a shelf . I hope to have it ready to run the 2010 land speed racing season . So 5 races will be a good test .

What I still have to find out is the valve springs . They are critical to an engine turning 14000 rpm . So IF he can't find a spring that specs out . I will have to have them custom wound . 200.00 each spring . Only sold in sets if 16. I did some math but ran out of fingers at over 3000 dollars for valve springs .
 

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0.5 mm is the most you can shave off the head and still be safe which is .019 inches so your good for what you wanted to take off. I would see if www.blackdiamodvalves.comhttp:// has a spring for you. The make tons of racing bikes and land speed setters. It's what went into the head Kibble White built.
 

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X:

I've got the 12:5 JE pistons and a ported and polished head (done on a flow bench by someone who knew what they were doing. Stage 2 jetting.

Thing runs a lot stronger. A lot more torque and at least 5 more mph up top.

I'm thinking of the 31mm keihins.
 

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I knew it was only a matter of time before we started seeing this. FI does have its advantages, but on carbs you can do alot more for less.
I would love to see some dynos of a stock engine that has had internal mods done. I think these little engines have so much potential. Ahhh I see our babies growing up!
 

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X, I really like what this is sounding like. The only thing I would think about is how this will skew your future mods, eh? It's easy to take off metal, not so easy to put it back.... So if you have a plan, and a design for your engine, "To the end", to completion, I'd say deck it and be done, just make sure you're never going to need that metal back (turbo????)... Keep us posted, eh?
 

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Discussion Starter · #13 ·
I definitely have a plan . Most of it involves letting a professional build the engine and leaving him alone to do it.
This is the engine I ride every day to work .
That is why I was thinking Deck it . Not shave the head . I can always get another cylinder block . Heads I like to leave alone metal wise . The more aluminum up there . the better the heat dissipation . Besides this is the stock engine .I am just tinkering while fixing it .

hi-tech said:
Must be nice to have two engines.. How u manage that? Did u buy a wreck ninja?
It would be nice if I planned this one . I budgeted for the race engine . Doing the stock engine is out of necessity
 

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Discussion Starter · #14 ·
I got my engine back together . I did not port the head . Just clean it up and laped the valves .
I did have a machine shop take .254mm of material off the top of the cylinder block. I put everything together with new gaskets .

When you remove material from the block or usually the head . Like a head gasket repair or valve job . You change the cam timing.

You see by removing material you move the camshaft down closer to the crankshaft . By changing the distance between the cam and crankshaft . you make the chain a little longer. Not enough to compensate for by moving the gear one tooth . But like 1/4 of a tooth .
Depending on the design of the engine you advance or retard the cam timing .
In the case of the 250 ninja it retards the cam timing . Or moves the point where the valves start to open to a later time .
I do want to retard my Exhaust cam but not my intake cam . SO I left the exhaust cam in the stock location on the adjustable cam sprockets . And Advanced my intake cam about 3 degrees . This ends up with the metal removed from the block ( that raises the compression ratio because the pistons stick up more .) And the exhaust cam is retarded 3 deg and the intake cam is in the stock location .

I still have to put the bike back together but I have tested the compression and the results were 170 psi on # 2 piston and 90 psi on #1 Now I have 185 psi on both cylinders.
 

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Discussion Starter · #16 ·
I think it is OK just 10-15 psi more than before. I can retard the ignition some Now that I have Ztrack s ignition system
 

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I think he was referring to the 90/170 combo. IIRC, Racer said that he had that issue of low compression because of valves not seating fully? I certainly hope that the #1 wasn't that low "just because".
 

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Discussion Starter · #18 ·
The intake and exhaust valves on number one where leaking. The valve clearance was spot on . So that sorta rules out bent valves. After lapping they held carb cleaner for a couple minutes. The bike ran OK. I wounder if they ever where seated in the first place.
 

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X, am I miss reading your post or does it say that #1 is 170, and #2 is 90. Is there supposed to be an extra 1 in front of that 90, or why am I being slow?
 

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Discussion Starter · #20 ·
When I went to install the adjustable sprockets .I wanted to measure the compression before and after. So when I got back from the drag strip I checked the compression . # 2 cylinder ONLY had 90 psi . it took about ten revolutions to reach that pressure. #1 measured 170 psi in about four revolutions. There should be a 1 in front of the 90 but that is the problem . I had about half the pressure in number one then number two.

The bike ran fine and went faster at the drag strip than ever before so I was shocked .

I discovered leaking valves and fixed that. I also cut down my block to raise the compression . now I have over 180 psi in both cylinders and it only takes a couple revolutions of the engine to pump up to that pressure.

I got the engine running last night . I still have not gotten the bike together . Or balanced the carbs . That is for today . But it sounded very good . So far
 
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