Racer X engine rebuild.

[Racer x]

I thought I would start this thread to help with questions regarding first gen engines, IF anyone want a photo of something say so . I will post up what I find. First some history on the engine.

I have a 1988 ninja 250 with 139000 miles. It went through three motors to get that mileage. I also was given a 2003 ninja with a salvage title. The motor from that bike is in the 1988 and makes a knocking noise. I used most of the 2003 bike to make a perfect bike. But I need a motor. SO I will see what I can fix.

This engine is from some where and had about 25000 miles on it when I got it. The rings where stuck with carbon and it had no compression. I did a port and polish job on the head and and put in a bunch of used parts and managed to go 106mph with no fairing,in the heat of June in at Maxton . BUT when I got home the oil was full of metal copper flakes, That indicates a bearing failure.

But it ran really well. lets see if I can fix it and how much it cost. I dont have the money to buy a new motor.

[alex.s]

25k miles you say? i'm kinda interested to see the condition of the cam chain and guides at that milage... when you are in there maybe you could measure the cam chain?

[cerberusrex25]

I got a question for ya. My engine has timing issues, every time piston #1 goes to TDC, it hits the Intake valve, any idea what could be wrong? Also the cam chain skips once in a while ( even though it has a brand new tensioner), could they be related?.

I was going down the threads when I saw this and thought " I should drop racer x a line one of this days" and then saw this, is like fate want ed this to happen. Thanks in advance for the answers, if you got them.

[Motofool]

Great thread, Eric; thanks.

Just take many pictures as you go.

It has been told many times that is cheaper to buy used than to rebuild these engines; however, in my opinion, the re-building experience will be priceless.

This reference may be useful to you:

http://www.dansmc.com/mc_repaircourse.htm

[Racer x]

The last one of these engines was sold in 2007. It will only take a short time befor the used engine option is gone. I sereously have no money for this project. But I have three engines than have similar problems with knocking sounds. I will strip the engine and see what is going on. I need an engine to sell or ride the 1988 bike so it will be worth the value of the bike to fix the engine.

[davenay67]

Originally Posted by Racer x

The last one of these engines was sold in 2007. It will only take a short time befor the used engine option is gone.

These bikes get crashed a lot more than most because of the high volume of new riders, so I am hoping there will still be a decent supply of engines available for a while yet. A production span of 20 years doesn't hurt either.

Great thread....I am very curious to see what is ailing your motor, and if it is a common issue.

[Racer x]

Originally Posted by davenay67

These bikes get crashed a lot more than most because of the high volume of new riders, so I am hoping there will still be a decent supply of engines available for a while yet. A production span of 20 years doesn't hurt either.

Great thread....I am very curious to see what is ailing your motor, and if it is a common issue.

But the low cost sends them to the crusher.

[greg737]

25k miles you say? i'm kinda interested to see the condition of the cam chain and guides at that milage... when you are in there maybe you could measure the cam chain?

Also the cam chain skips once in a while ( even though it has a brand new tensioner), could they be related?.

From what I've read here and on the other forum it seems that cam chain wear (and resulting stretch) is highly variable from one bike to another. But it definitely happens.

Also, when the cam chain wears and stretches it does it in spots along its length rather than uniformly throughout the entire chain (this is confirmed by a few forum members who've measured their worn chains). This causes it to go tight-loose-tight-loose as it goes around the drive gear and the camshaft gears. The tight-loose-tight-loose situation causes it to "lash" at the cam chain tensioner, making a knocking noise.

It's not surprising that the cam chain tensioner doesn't stand up well to this abuse. The cam chain tensioner was designed to maintain proper tension on the cam chain in response to engine accelerations and decelerations, which happen (relatively) smoothly and slowly compared to the high-frequency of the tight-loose-tight-loose lashing effect of a partially worn and stretched cam chain.

Bottom line: I believe the engine problems people regularly attribute to the cam chain tensioner are actually related to or entirely caused by an irregularly worn and (as a result of that wear) stretched cam chain. So replacing the cam chain tensioner without dealing with (i.e. replacing) the worn cam chain is pointless.

[Racer x]

I tore the engine down tonight. It looks very good inside, The owner did a very good job of maintaining the bike. It looks like a crank bearing is scuffed and the rods have a little. But over all it is great.

[Racer x]

more photos

[Racer x]

This is the cam chain and the tensioner. this all looks perfect. The tensioner is a little worn
There are a couple indentations from the ball bearings that I don't like. I will look into a manual one, Or at least a new one.

The cam chain stretch spec is 127-127.4mm max is 128.5 mm that is 20 links. a link is each pin so ten outer plates or twenty pins.

I had to take a look at that really close. This chain is exactly 127mm for 21 pins.It has a long way to go.But why would it be short? What am I doing wrong? except drinking beer.

[alex.s]

is there a service interval or spec for the chain guides? im guessing no right?

[Motofool]

Originally Posted by Racer x

.....I had to take a look at that really close. This chain is exactly 127mm for 21 pins.It has a long way to go.But why would it be short? What am I doing wrong? except drinking beer.

That is perfect!
You measure 20 spaces of 1/4" each between pins, which includes 21 pins

You are a very clean and organized mechanic, Racer x

Thanks for the good pictures

[Racer x]

You have to be that way to build engines. I also am trained as a watch maker. That helps

I will put together a parts list of things I think I will need. Gaskets and bearings but I need to measure things first . I will also need to get the ends off the crank. I have the tool for that but it is still tough.
The rod bolts all get replaced every time you tighten them and I guess some O rings . I use cheap cycle parts

[MCPhotographer]

Quick rundown. Bike has about 11980 miles on it. Was having problems with idle, could not get it to stay constant, and it would die when coming to a stop in traffic. Pulled the carbs twice, Chem dipping it the second time. They were very clean and had been pulled once before about 5k miles earlier. After the problem remained after the first pull, I replaced the float valve needles. Same problem. I bench synched the carbs so I did not think a carb synch was needed, or not that is wasn't needed but that it wasn't the source of the idle problem. After some research it sounded like the valves needed adjusting , which I already knew they did. The prices for valves from local shops is ridiculous ($400 was the low quote I got). From the mechanic I know who does side jobs, he wanted $250. I'd never done valves before and while I was apprehensive, I really wanted to pay someone the first time so that I could watch them do them. I've learned the hard way that stuff like this is usually not better to guess/try your hand at, unless you're willing to pay the resulting tab when you $@#% it up. Contacted him around Thanksgiving and he said he was busy for the next month. Contacted him again...vacation. So I did it. Not difficult but the torque specifications on the adjustment nut have me wary. Valves were SUPER tight. After the 1st adjustment it was back to idling normally, so that issue was solved. However, and here's the problem I have now, the engine is ridiculously loud. It's also doing this hesitation in higher gears causing an on again off again power fluctuation. I reinstalled the stock CCT. No joy there. I bought a Krieger manual cam chain tensioner and installed that, but while the noise was lessened, it was still extremely loud. I read that noisy valves are happy valves, but the noise seemed/s excessive. And still the power fluctuations. I checked the valve clearances again. They were all within spec. I relayed this to Mark Krieger and he was extremely helpful with trying to remedy my issue, however his conclusion was that the tensioner had run out of adjustment and that I would need to grind the rocker arm to adjust the Cam Chain further. So yesterday I open her up again because I wanted to check to make sure the cams were still in time. They are perfect. So I pulled the right side case cover off, but I still have no idea which rocker it is I need to grind. Pretty sure I need to remove the clutch to access it based on the diagram. However, before I do this, I have the suspicion that this will NOT solve my problem as the chain seems to be stretched. I noticed this the first time I adjusted the valves. As I turned the engine there were spots that were really loose and easy to turn, and real tight difficult to turn spots. I read this in another post, which seems to be my exact problem:

Originally Posted by greg737

From what I've read here and on the other forum it seems that cam chain wear (and resulting stretch) is highly variable from one bike to another. But it definitely happens.

Also, when the cam chain wears and stretches it does it in spots along its length rather than uniformly throughout the entire chain (this is confirmed by a few forum members who've measured their worn chains). This causes it to go tight-loose-tight-loose as it goes around the drive gear and the camshaft gears. The tight-loose-tight-loose situation causes it to "lash" at the cam chain tensioner, making a knocking noise.

It's not surprising that the cam chain tensioner doesn't stand up well to this abuse. The cam chain tensioner was designed to maintain proper tension on the cam chain in response to engine accelerations and decelerations, which happen (relatively) smoothly and slowly compared to the high-frequency of the tight-loose-tight-loose lashing effect of a partially worn and stretched cam chain.

Bottom line: I believe the engine problems people regularly attribute to the cam chain tensioner are actually related to or entirely caused by an irregularly worn and (as a result of that wear) stretched cam chain. So replacing the cam chain tensioner without dealing with (i.e. replacing) the worn cam chain is pointless.

Would this be what's causing my power fluctuations? Can someone who is familiar with this and possibly has dealt with this before, look at my video and tell me if my suspicions are correct? And if the Cam Chain is toast, I know I will need to pull the engine and replace the chain. I haven't found a write up on this yet, does anyone know if one exists? Thanks in advance to all that took the time to read and respond to this.

My chain
https://www.youtube.com/watch?v=K2ljecz4euc