Dennis the Deathtrap

[DXZeff]

As a Christmas present to myself, I decided it was time to replace my worn out bike with a new one. Where the previous bike used the cheapest kit available from China, the new one uses an improved kit from gasbike.net, the Raw Racer II, as this seemed to be the best value for money at the time. Thus far it seems to be pretty ballsy, top speed is unknown but there's way more torque than the old bike ever had.

So anyway, meet Dennis III; (Don't ask about Dennis I, that was an autowheel, it sucked)

http://dxzeff.com/trash/d3-full.jpg

The engine. This engine has a larger piston than the regular China kits, the cylinder and head are a single piece. Carb is stock (heard too many mixed stories about the upgraded ones and they seem harder to repair if something breaks) but it does use an upgraded air filter, CDI is also an upgraded one, all of these parts come with the kit, usually costing about the same as an entire engine kit anyway, so I think I got my hundred quids worth easily.

http://dxzeff.com/trash/d3-motor.jpg

The exhaust is mine though, the old engine doesn't really like this one so much and the one I was using proved far too loud, annoying the neighbors more than I'd like so this one seemed like a good middle ground. Note how I found a use for the stock chain tensioner, someone else must surely have done that already.
Also note the CNC sprocket adapter, that won't be staying, don't know if I just got a bad one but it didn't fit as well as I'd like, I had to make my own shims but it still keeps coming loose, both around the hub and the sprocket itself regardless of threadlocker, my wheel is ruined.

http://dxzeff.com/trash/d3-pipe.jpg

That's the pipe I fitted at first, it was nice but I'd rather not fall out with the neighbors. Lost a tiny bit of power by changing it as well as the rather nice noise it made, but oh well. I might have carried the name 'Dennis the Menace to Society' since the autowheel I built, but this was an excessive one that was likely to end in some kind of noise ordinance violation I'd rather not contend with.

http://dxzeff.com/trash/d3-oldexhaust.jpg

As I never posted a full picture of it, here's the old one, Dennis II, made from the cheapest and cruddiest parts available. By now it's a mash of more than one kit.

http://dxzeff.com/trash/dennis2.jpg


Not sure what to say really, at some point I'll strip the old engine down to try and find that mysterious loss of power but I'm waiting on gaskets coming from China as I'd like to keep it running just for fun and the fact it served me far better than I could have hoped. Suppose I could close off with this;

Going back with the old bike proved that the road was slippery due to oil, which was mysteriously there for some reason, and I'm sure has nothing to do with someone regularly riding a beat up 2-stroke that leaks oil everywhere on that roundabout. Wasn't hurt, bike wasn't damaged, but I'll be looking into why the clutch didn't disengage, probably need to adjust the cable. Either way, this new one should make pulling the heavy trailer around much more pleasant than before. It's not as nice as some of the builds I've seen around here, that's for sure, but it should do its job well enough for me.

 

[PeteMcP]

Welcome to a fellow Brit.
Well, that spill could have ended worse. At least you laughed it off.

 

[DXZeff]

Hah, yeah, was starting to think I was the only one here from GB.
It'll take more than a fall like that to stop me yet, in years gone by I did a lot of mountain biking, also figure skating, they both kinda teach you to just get back up and try again, sometimes you just have to throw the bike and take the fall as was the case here. That and I'm used to riding around on what can likely be described as tetanus waiting to happen, the design motifs of the car in your avatar certainly remind me of the era that came from, this is my usual ride when I'm not using a motor;

That's the fancy one, that one has electric lights, the other one I have uses kerosene. Wouldn't mind finding a period correct autowheel for them some day, but as if that's ever gonna happen.

But anyway, the gas bike, might move the engine to a better frame eventually, nothing much will change otherwise.

 

[DXZeff]

Update: Changed to a smaller, fatter frame that isn't riddled with problems, same configuration, also another wheel ruined by the hub adapter despite making a woodruff key for it - it just tore the shim, guess I'll just write that off and use the dumb rag joint on a new wheel, these adapters are totally toilet, not worth the money... May actually be OK if you're on like a 50cc without much torque and are willing to make a key way in the shim and your hub, but it didn't work out here.

Thought something was wrong with the motor or the carb, engine simply wouldn't fire, we messed with things for a while and eventually got it to start, but it wouldn't idle and only seemed to 'fire' intermittently (this probably didn't help the afore mentioned hub adapter). Pulled out the plug, it was wet, immediate thought was an electrical problem. High Performance CDI seems to be busted, with less than ten miles on the clock. Wonderful. I read a few threads saying this happened to people in the past but always thought it couldn't be that likely, apparently I was wrong, fair enough, learn from it and move on. At least it happened on my street rather than however many miles away with a fully loaded trailer on the back, it remains to be seen if there's any loss in performance versus the supposedly better CDI that died.

 

[DXZeff]

Whilst I'm not a fan of bumping my own threads, I do feel it is time for a further update, especially as I think I'm the first (or at least among the first) to be using the Raw Racer II around here. At this point I am convinced that any part with 'improved' or 'upgrade' written next to it is a complete waste of time, as far as these kits go, perhaps I should have just ordered another 'cheapest on eBay' China special after all.

Look at the state of this thing now;

All those stock China parts. The carb it came with? No good. The 'better' air filter it came with? No good. The exhaust? No good except that really loud one, but that's not suitable for where I use this thing. Even the fuel petcock had to be swapped for a brittle old one from a cheap kit due to rubbish fuel flow.

So much tampering and it still runs quite badly, I've been through everything right down to tampering with the magneto and spraying ether at possible leaks, nothing, the best I can do is wind up with a rapidly overheating engine. It pulled its first trailer a few days ago, I figured the engine was maybe running rich because it was 4-stroking quite a lot, but that went away and didn't really concern me until I'd climbed the hill and it began pinging instead before losing power, shut it off, it had only been running for about five minutes at fairly conservative speeds. I didn't expect great performance on a fairly new engine, but the old one went right into pulling way more weight than that without issues in the middle of summer no less.
Walked most of the way home.

Further testing showed the throttle was hanging badly, acceleration wasn't too bad but the engine would ping if I went at full throttle. This was on the richest setting on the needle, so I moved up a few jet sizes, too big initially as that's easier to work from. This did what I would expect, made lots of smoke and lots of 4-stroking, drop a couple of sizes to an 0.76, seems about right, mild 4-stroking and... also pinging and the rapid overheating is back, as well as that smell of 'something is going to melt' and a heat haze from the motor. A rich running engine shouldn't really overheat like that, especially as I wasn't pulling a 200lb trailer behind it any more and it was icy outside.
All in all, I'm not convinced this design can get rid of the heat fast enough, I mean sure it's nice to have the larger piston and the increased torque, but I'm fairly certain it's not going to last long. I've adjusted it to at least run smoothly, but I will probably be pulling the top end off and replacing it with a generic slant head and 40mm jug because this is just ridiculous. Sure, it probably will improve when the engine is fully broken in, but I'm not even sure it will get that far, here's hoping that when something inevitably melts it doesn't take the crank case and such with it so I can just replace the top end and be done with it - no doubt this will necessitate I dig out the old jet again, but at least the rest of the pieces should bolt straight on like normal.


On a slightly more lighthearted note, I needed my spare petrol can for something, but it had gas in that was over a year old (closer to 2), with nowhere to dump that I threw it in the old bike to see what would happen, given that thing is retired now, surprisingly it doesn't seem to care all that much, I thought it would run much worse on that yellow goop than it does. It's burned through pretty much all of it by now, there were was barely 1/4 litre in there. Obviously I don't recommend doing this if you care about your motor, but the old one is basically just something to play with at this point.