You Know

It's going to be a good day when you open your pop tart and there is a motorcycle on it.

All I Can Say Is

COOL

A Matter of Timing

Getting the cam/valve timing right. 99.5 % of my engine building experience is on two stroke motors. Almost everyone who has owned dirt bikes or two stroke street bikes had to tear down the engine for an over pop or rings. You had a couple of options, you could pay someone to do the rebuild for you or you could do it yourself.

I have had a ton of two stroke bikes, mostly street bikes. Most of them were Yamaha RD 400's and a couple of Kawasaki H2's. My dirt bikes where of the Suzuki RM 125 and 250 variety Those of you who have owned these bikes, usually messed with the engine to get more performance. Or in the case of the 79' Daytona Special had the two piece crank split in two on you. I have no idea why Yamaha went with this set up for the Daytona, but in the end you would have to replace it with a single piece crank from a 78' or earlier RD. My collection of RD’s were in various states of repair, and I was constantly messing around with them so I became familiar with their motors in a hurry.

I do not have a whole lot of experience with four strokes other than giving them tune ups, adjusting the valves and carbs every now and then. This is the first four stroke rebuild I have done other than a lawn mower engine or two. And the biggest concern I had was timing the cams. This procedure turned out way easier than I thought it would, at least on this bike.

After tightening the 10mm bolts to 29 ft. lbs. the 6mm bolts to 7.2 ft. lbs. and the head nuts to 14 ft. lbs in the proper sequence, it was time to install the cams and line up the timing marks. The intake cam has a I on it for intake and the exhaust is marked with an “ex”. Then you need to Align the flywheel T mark with the stationary pointer on the crank case.
Next step is to rotate the exhaust cam to line the timing mark with the left side cap mark. Do the same for the intake, put the cam chain on and adjust the whole shooting match till both cam marks and the timing mark are aligned in their proper positions. Torque the cam caps and timing chain guide bolts to 7.2 ft. lbs.

Now it’s time to reinstall the tensioner assembly. First remove the blind bolt, then insert a screw driver into the blind bolt hole and turn clock wise until it stops completely. Install the tensioner and gasket and torque to 8.7 ft. lbs. pull out the screw driver to release tension and set the blind bolt to 4.3 ft. lbs. Reinstall the valve cover and gasket (not in that order)and you’re ready to install the engine in the frame.

Just a case of following the manual and every thing fit together like a glove. This procedure was not too bad on this single with overhead cams, but I suspect it is just a tad more complicated as the number of cylinders increase. Next is the electrical and charging systems, I suspect this is what took this bike out of service in the first place. It basically needs to completely rewired as most of the wiring is shot.

Till Next Time......................

Back in Running Order

Not my XT, no that wouldn’t make sense, I have not finished procrastinating on that project. We revived Curly’s YZ yesterday after a engine tear down to take measurements and to replace any parts that were in need of replacing. All it really needed was a new set of rings, some new reeds, a powervalve cleaning and a good old carb cleaning and adjustment. The bore was within specs for the .20 over pop that was already on it. The piston looked like new and measured out that way.
It also was a chance to brush up on our drilling and tapping skills. I cannot remember ever snapping off so many screws and bolts. We must have broke off about twelve altogether. Most were all securing body pieces and a couple on the engine cases, so there was not too much drama.No need to crack out the old Helicoil set.

The bike was a bit dirty, mainly because it is a dirt bike. But the frame has quite a bit of boot rash and a few stone chips and such. My pleads to Curly to take off all her clothes so I could give the frame a good going over and a fresh paint job fell on deaf ears. He wanted to get the bike going in a reasonable amount of time, so figuring my bike is still not done, he did not want to wait till December to finish his. I had to remind him, though my bike is almost finished, the first thing I did was strip and paint it. At least all the parts look great.
He said if he was going to keep her, he would consider buying her a new set clothes and putting some make up on her. But he is just looking to turn her around for a quick profit. So after we snugged everything up, added the proper amount of fluids, she started on the third kick. I love two strokes, they are easy to work on, and easy to trouble shoot.
Here are a couple of pics of Curly putting her through her paces. So after about a hour of running her up and down the street to make sure all systems were operating properly and to promote goodwill towards Curly’s neighbors, we figured we had the old girl pretty much sorted out. She ran like new, power wheelies in the first four gears, even with a couple of fat guys pouring the coals to her. I almost forgot how fast two stroke two fifties are, even twenty year old ones.


Till Next Time...............................

If There is a Way

For me to take even longer finishing my bike, it would be helping a friend rebuild his new turd. This just happens to be the exact situation I am in right now. Obligations to others seem to have a profound impact on getting the projects I have sitting around done. They tend to stay sitting around even longer.
Curly, just recently acquired a 1987 YZ 250 from a mutual friend. It is in pretty rough shape by the looks of it, but turns over freely and seem to have good compression. All it probably needs to get it running is a good carb rebuild and cleaning. But there are other issues like the chain and sprockets have seen better days, and the plastics are in bad shape. The tires are also shot. This bike pretty much has been sitting around since 1995 so a tear down and complete going though is in order.
So I made Curly a deal he couldn't refuse, I would help him put a good coat of wax on his turd, if he would reciprocate in kind. My bike really does not have a whole lot left to do to finish, but sometimes a couple of friends working towards a common goal is the best way to get on the stick and get your projects completed.
So in addition to the completion of my bike, I will have another bike to work on and write about. We popped the top end off and things look pretty good so far, just take a few measurements and see where we stand.
Should be fun, stay tuned.


Till Next Time.........................................

Remember your first mini bike?

I still have fond memories of the old wildcat minibike that hooked me into a life long love of motorcycles. Getting to relive that moment again through the eyes of my boy, was just as good a feeling for me as when I first laid eyes on that old wildcat many moons ago.

I had the pleasure of reliving a first time bike again the other day. A friend of mine called and said he was going to surprise his boy with a KDX 50. He came by and picked me up and we made the trip up to pick up the bike while his wife was running errands with their kids. When she returned home we were waiting with the bike. The look on Levi’s face says it all, THAT’S MINE REALLY?????
He could barely wait to ride it of course, so we loaded it up and drove to a nearby field to give young Levi his first taste of two wheeled fun. After a few words of caution from his Dad, he was off like a shot out of a gun. Like most kids first time on a minibike, it was WFO for Levi right from the start. It’s a good thing this bike comes with a throttle limiter, because the boy would have probably rode right though a near by fence. Absolutely no fear from him, until the inevitable first crash. He got up, dusted himself off and was on his way again, (at a somewhat slower pace)

We don’t get to go back in time unfortunately, but at least we get to experience what it feels like to be a kid again with moments like these. Dad couldn’t resist testing out the little fifty for himself, I think he had as much fun as his boy did.

Till Next Time.............................

Winter, Spring, Summer or..............

I don't think it has ever taken me this long to rebuild a bike. But after back burnering this project time and time again, progress is slowly being made.
Why spend twenty bucks when you could spend twenty cents.If a picture speaks a thousand words, this one does not speak well of my welding skills.
I whipped up a valve compression tool out of a couple of washers and bolts that I cut the heads off of. I welded the whole shooting match together, abra cadabra, presto and nothing up my sleeve, I saved my cheap ass some green backs. It also looks as if a monkey welded it together.It actually works great, it took me all of five minutes to compress the springs and replace the keepers.
More to come, I bet you can hardly wait.

Till Next Time..................