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Discussion in 'Some Assembly Required' started by 79thunder, Feb 11, 2018.
Great build so far!!!
Thanks! I was hoping some locals might recognize it !
Not the most difficult riding that I have done, but it does represent the type that I enjoy.
Challenging enough to be fun, but not too risky when riding alone.
I don't choose to be alone, but I'm also perfectly happy that way too, I think I only saw 1 or 2 other riders this year in that area??
Your more than welcome to come have a look anytime. -Maybe PM for details?
Crap ! I should have known that was coming !! You guys are pushing my computer tech skills already. I'll work on it.
The sound kind of surprizes me. I think it has a little deeper tone than I was expecting.
Maybe a touch louder than I would like, I can maybe tune that later. It is fairly smooth, not raspy?
Doesn't really sound like a sportbike to me at all. I'm more than OK with that !
Thank you very much.
Yours looks ridiculously fun !!!
I'm going to revisit this little guy briefly.
If anyone is considering buying a motorcycle equipped with one,
They may pick up a little information here.
Also, in the Thumper section of this forum in either the
Pitster Pro LXR 250f or in the CSC RX3 threads.
This is the original NC250 Zongshen from my RX3.
I'll be honest, looking at that picture almost makes me sad!
I wish that I had the time, room and another bike to put it in.
It has had 3 oil changes and 3 valve adjustments, has zero leaks and seems to be pulling stronger all the time.
I was not disappointed in the performance of the engine in the least.
A 250 cc fuel injected, liquid cooled, 4 valve 4 stroke with a 6 speed trans.
Putting out 24.8 hp.
It is Zongshen's own, it is not a clone or copy of any other engine.
Now I hate simple hp number comparisons but to put that into perspective, here's a few of the other very similar engines.
Honda CRF250L @ 19.6 hp
Kawi KLX250 @ 19.5 hp
Yami XT250 @ 17.5 hp
Yami WR250 @ 24.8 hp ( I know, I know uncorked it could be 30hp)
Pitster Pro claims 32 hp using the same Zongshen NC250 engine.
As you can see the engine is right on par with, if not above many of its Japanese contemporaries.
I am doing my best to compare apples to apples here.
All of the above are modern 250cc 4 or 5 valve, liquid cooled fuel injected engines.
I did leave the raunchier race orientated bikes out.
Numbers aside, in my experience, the NC250 feels stronger/faster throughout the entire rev range than the Honda, Kawaski and the Yamaha XT250.
I also think it is much smoother at highway speeds.
It is kind of a smooth, tractable power though, you can run it at wide open throttle.
Fun, but not scary.
The WR250 is faster, the top end hits harder. Is it the tune? the chassis? Both? not sure.
I honestly think it's because it has 1 more valve.
The engine that I believe that the Zongshen NC250 comes closest to in terms of performance and
characteristics is the slightly obscure Yamaha TTR250. (only Aussie's and Brit's seem to know of it/own one)
Which is basically a WR engine with a 4 valve head.
(and air cooled, I know!)
I'm not certain if that will help any one, but there it is, my two cents.
What should be glaringly obvious is that all of the above engines come installed in relatively (300-350lb) light weight dual sport motorcycles.
I think that is the perfect platform for this engine.
Check out what Navin and the others have to say about the Pitster Pro LXR in that section.
Zongshen chose to install that engine in a slightly heavier (385lb with gear) Adventure bike.
And damn it, it almost works !! It's great off road, on gravel roads and secondary highways.
This is where it starts to lag. Way up that hill.
What you cannot see is the soul sucking, mind numbing, 75 mph headwind !!!
Nor can you see the '77 Winnebago Brave, box-on-wheels I had to pass going up that hill !!!
I later learned that this stretch is notorious for wind !
I think most bikes less than 650cc's would have struggled.
Don't misunderstand me, I think that was my favorite day out this year. I covered over 900 kms.
The bike pulled those hills just fine at around 100km/hr. The wind really tried to suck the fun out of it though.
The simple solution was to get into the back country, into the trees and mountains and enjoy the scenery, which not only gave me a break from the wind but a fresher perspective.
Sometimes, if it's not fun, or at the very least, enjoyable, then stop doing it...
Some of you can go quit your day jobs now. You'll thank me for it later.
In the meantime....I've got some packing to do !
I like what you have created 79Thunder. How's about a lil more info on the device your using to hold the front wheel while it's on the platform. Looks like a modified screw jack with welded on attachments....
That motor is a sweetheart that runs pretty much exactly like a 2005 Big Block Husqvarna TC250f. Its not fast compared to a modern 250f, but it works well and pulls from the very bottom to the top with a flat delivery that hooks up.
Thanks Navin, I know you've got plenty of laps on your LXR and you've thrown your leg over more than a few bikes.
I think some of your older posts on the Yamaha R3 helped convince me that this engine was what I was after.
But your sig reminds me, I might have to change my thread title to XT3 the 42hp LXR250f killer !!
Your write up set a good example for everyone. Get to the point, but don't leave anything important out. Good fab skills.
And that is exactly what that is. I posted it in jaglite's excellent project build table thread on about page 3.
There is also the bike jack and the table. I'll try a link here --->http://advrider.com/index.php?threads/bike-project-build-table.1013608/
I did not do a how-to, so if you need more info, let me know.
The pictures are all I need. Thank you.
Wow ! Thank you.
I'm a pretty quiet guy in real life so, That felt like far too much.
I think I would have preferred to post up 2 pictures.
"Before" and "After" and let you guys figure out what the hell I had done.
Besides, I'm not quite done yet ! But I don't think it will drag on for 100 pages !
Thank you ! That means alot. There are some mighty fine projects in your garage as well!!
Experienced bike builders can skip this post.
Earlier, I blazed through the portion where I fabricated and installed the engine mounts.
For those who might be unfamiliar with the process, or for those of you bored out of your minds.....
Here is how I approached the mounts on my bike. I'm not saying it is the right way.
There are several ways to skin a cat. (though most will make you puke!)
I built the engine mounts in the order shown. (1,2,3,4)
#1 is the most critical and sets the height relationship between the countershaft sprocket and the swingarm pivot centerline. It also determines the position of the engine side-to-side within the chassis. (aligning the countershaft sprocket to the rear sprocket) it also seems to support most of the weight.
#2 Determined the angle that the engine sits.
It also kept the engine parallel to the chassis and level side to side.
Once #1 and #2 were done the engine was pretty much locked in place and fully suspended.
I did not want to use #3 to determine engine position because there is a bushing inside. I didn't want to "bind up" the bushing, have the engine move or place stress upon the engine or frame.
#3 and #4 were fabricated a little later.
You obviously cannot see it, but mount #3 is bolted to the chassis using a pair of pre-existing holes.
I might not ever need it, but it makes engine removal easier. The #2 brackets are also removable, which gives me a ton of room if necessary.
The picture also gives an idea of the skid plate to engine oil pan and filter clearances.
You certainly thought it out very well.
The order you chose for engine mounting is very important to have a strong connection without prestressing the frame or the engine.
Excellent example of thoughtful design and fabrication.
I agree 100% with your view to not attach the skid plate to the engine.
That is practically a guarantee of engine case damage if the bike is ridden off road at all.
Also many engine cases crack at the lower forward mounts where bolted to the frame.
A strong skid plate is great except that it will transfer all the stress from a hard impact to the frame, and that is usually right where the bottom engine mount is.
Your design uses suspended engine mounting with a strong under frame to take any impacts and not transfer them to the engine.
All adv, dual sport, and dirt bikes should be designed this way.
I haven't done it yet but I am going to add a layer of UHMW-PE plastic (0.125" or 0.1875") to my aluminum skid plate to give it more strength for point impact (a sharp rock) and as a glide to slide over rocks.
Aluminum sure doesn't slide well over rocks even though it is smooth.
I think because it is soft the rock digs into it.
I mention it because your skid plate isn't real thick and the sump is pretty close so if you found yourself hung up on a sharp rock in exactly the worst place, between the frame rails and under the sump....
Just something to consider.
I'm looking forward to seeing pictures of your bike
Thank you very much !!
I'm not a bike builder, this is my first.
There are certainly far more talented and knowledgeable guys in this section doing far more creative and extensive bike builds.
I'm not even certain that mine belongs in here.
The reality is that I am now an orphan.
It's no longer a thumper, so I don't fit in there..
It's not 100% CSC RX3 anymore so that's out..
It's not exactly a twin powered bike that is from Japan, so that section is out. (but, the closest affiliation I have)
You guys have made me feel welcome here, thanks !
As far as the skidplate goes, I'm not 100% sure which way I'll go yet.
The plate that is on right now is being used just for a template.
I had planned on 1/4" aluminum. That is what I have on my other bike.
You are correct, aluminum doesn't slide that well!
I had also envisioned adding "wings" to the lower sides of the plate.
I don't think that I will now. The engine is very nicely tucked in behind the cradle.
The crash bars will protect the engine side cases.
I have thought about using some 10 guage steel plate, I have a lot of it here.
Of course the downside is the weight and corrosion.
Painting or powder coating a skidplate seems like a waste.
Using UHMW might be a great solution !
I think a replaceable insert would work very well.
One of the CRF500L builders used Titanium.
That also might be a great option. I have no idea what a 1' x 2' piece of Titanium would cost or any idea where I could get some.
To me it still seems like a if you have to ask, you can't afford it material.
Maybe I'm way off base. Worth looking into at least.
For reference, there is about 1/2" between the skidplate and oil pan. My sharpie marker and 10mm socket keep rolling under there!
I think that most of the initial impact force will be at or near the front crossmember.
Pretty hard to predict what can happen when bouncing down a trail though.
I could maybe add another crossmember behind the oil pan.
I'll think it over. I'll come up with something. It would probably be just fine the way it is. But..
I do need a bike that I can ride with a little wreckless abandon on occasion.
You'll need to load the video onto Youtube or somewhere similar and then share it on here, you can't load videos onto ADVrider.
I'll work on that.
I've changed my mind, It does have a raunchy little sportbike sound!!
Fairly quiet at idle and lower rev's, but when I crack the throttle.....well I guess you'll have to wait.
Hope you're a patient guy.
I grabbed a couple more pictures of the air box. While I could have used pod style filters inside the box, I chose to use the stock filter from the Yamaha R3.
I know it is sized correctly (cfm) for this engine and is easy to find replacements. I'll install a fresh one before I hit the road this spring.
Visual inspection and replacement couldn't be any easier.
It was a real chore on both the factory RX3 and the Yamaha R3.
The raised "top hat" section is slightly shorter than the air filter.
Which squishes the air filter down against the foam seal of the filter.
I also applied a secondary foam seal around the perimeter of the lid which seals everything up nicely. The air box has the usual water drain and fittings for PCV, etc..
I am a big fan of UHMW PE for skidplates; after having had Al and UHMW skidplates on various quads I would never go with a Al skidplate again. Just to give you a idea on my SxS I have 1/2" UHMW skidplates with built in nerf / sill protection and they have held up better than I would have imagined even after lots of time in Crowsnest pass in the rocks:
Thanks, I'm definately considering using a replaceable UHMW insert.