Advice for a possible rebuild (or second build) frame!

Discussion in '2-Stroke Engines' started by Hajuu, Mar 18, 2010.

  1. Hajuu

    Hajuu Member

    Hey guys,

    I've been working on my first build for.. what seems like a long time now and i've basically come to the point where I feel like the bike is a really limiting factor in every aspect that has made this project difficult. All parts of the bike were from a very cheap second hand bike I picked up, in poor condition.

    So now i'm thinking of removing the kit, and cleaning it all up and installing it on a new frame.

    If I post some exact names of bikes hopefully someone will know if people have used the kits with these frames before :)

    Or any other information.

    I think the first frame I looked at was the Avanti Voltage http://totallyspoked.com.au/images/uploads/Avanti Voltage.jpg but I dont really like the bikes with the non-flatbar frames.

    Thesedays however it seems like most bikes have these stupid dropbar frames, for some reason, and that the main frames I like are roadbike frames.

    Which brings me to the first question of, can you install one of these on a roadbike with high gauge spokes? Will durability suffer? It seems to me nearly any roadbike would do as they all practically have the flatbar frame, big wheels, and thin frames.
     

  2. AussieSteve

    AussieSteve Active Member

    Mike, what do you mean by 'flatbar' and 'dropbar'? Bicycles aren't my specialty.
    Do you mean? :-
    Flatbar = horizontal top tube
    dropbar = non-horizontal top tube

    After looking at that pic, I think that you do.

    Is 'Malvern Star' good enough quality?
    If so, a 'Malvern Star Octane' can be had, new, for $300.
    It has a horizontal top tube, 18-speed gears, linear pull brakes, double-wall rims, and alloy frame. They come in 2 or 3 frame sizes, the "L", (I forget the size in cm, just went to have a look but I've removed the sticker), is perfect to fit a HT engine, even with a shift-kit. No clearance issues.
    If you're interested, check out my album.

    These kits are designed for road bikes, 26" or 27". They drop straight in.
    You don't want skinny road bike tyres, though.

    I almost fitted my kit to my old 27" racer, but bought the new MTB instead.
    I got more fun out of leaving the old racer out the front and watching it being stolen through the curtains. Took 3 days, but I didn't need to make a 'Free To Good Home' sign.
    Should have video'd the theft - it was funny.
     
    Last edited: Mar 19, 2010
  3. Hajuu

    Hajuu Member

    Yeah got it in one Aussiesteve, i'm not sure why but for my money the dropbar frames are just much more effortful to ride.

    Anything is good enough quality to me, as far as im concerned practically any new bike has the longevity to last atleast a few years under normal circumstances.

    A racing bike frame does seem like a **** good idea, and ones in good working order can be had for cheap ($150 second hand). The main issue obviously is cost, and thats why I was looking at the voltage, as they're on sale right now for $200 new!

    What kind of tyres would you put on it, maybe those slightly wider hybrid semi-slicks which are smooth in the middle and have tread on the outside for cornering?

    I'm also going to do up an inventory at the same time and make a huge order to coventrys for all new mounting bolts and nylox nuts, is there anything specific I should ask for for ones that can be tightened harder than usual?

    Also is it possible to install a front suspension fork on a roadbike, or am I likely to have problems with that?
     
  4. AussieSteve

    AussieSteve Active Member

    The biggest problem with 'dropbar' frames is that a HT engine won't fit in them.
    That's why I bought the large frame version, despite being a short-***. I went shop-to-shop with a piece of string with two knots in it to measure the down-tube.

    Racing bike frames are very weak and wide tyres won't fit between the rear chainstays or standard forks easily.
    Not sure about front suspension, but even with it, you'll be building a bone-shaker. It won't be pleasant to ride very fast. Over 40kph will be murder for road vibration. Also, the low-profile of road tyres means potential pinch-flats. You really do need a bike that can fit decent tyres.
    My next build will be full-suspension. Front suspension doesn't help a whole lot on it's own. (Not when you're 51 years old, at least.)
     
    Last edited: Mar 19, 2010
  5. Hajuu

    Hajuu Member

    My concern is really more for improving handling, as on my current build the back wheel is very firmly grounded.

    Plus I figure one of these with a gel suspension seat on a shock absorbing post will make for a fairly comfortable ride, if you don't mind some vibrations :p. Vibrations arent a bother to me, strong part of the feel of the ride, I step off my bike shaking a little. haha.

    But yeah i'll go for a similar 'hybrid' bike or full mb.

    As for the drop bar thing, i've seen a lot of them with bars that aren't dramatically dropped, just on a small backwards slope.. These bikes barely had reduced area, but I find need conciderably more power to get going.
     
  6. Hajuu

    Hajuu Member

    Also: Bigger wheels/frame = Smoother ride at high speed right?
     
  7. AussieSteve

    AussieSteve Active Member

    Only if the tyres are equally soft. Believe me, a 26" mountain bike is much smoother than a 27" road racer, due to the high profile tyres on the MTB, before even considering the suspension. A road racer 'feels' even the cracks in a concrete footpath and any decent bump/pothole will pinch the tube easily. Even with 2.00" MTB tyres, I need 40psi in the front and 50psi in the back to reduce pinch flats on my local roads. Just the same, I've had 3 in 1000km, between the two bikes.

    I don't quite understand you on this - are you saying that if the top-tube isn't horizontal, it's harder to pedal?
    What reduced area? Don't follow.

    (I have had 3 beers - might be getting slow.)
     
    Last edited: Mar 19, 2010
  8. Hajuu

    Hajuu Member

    A possible candidate:

    http://perth.gumtree.com.au/c-ViewAdLargeImage?AdId=192935564

    Edit:
    Haha, sorry, as usual I wasn't very clear.

    They have a top bar that isn't quite horizontal, as you say, while the rest of the frame sits at about normal dimensions still.

    The area in which your motor sits seems to on quite a few of them be only marginally reduced on many of them, but I do still find them harder to pedal, but seem cruisier at higher speeds. I'll have a motor, so I obviously don't really need/want that cruisyness necessarily.
     
    Last edited: Mar 19, 2010
  9. AussieSteve

    AussieSteve Active Member

    Not sure why they'd be harder to pedal, might be a slightly different seating position. As I said, I'm no bicycle expert, although I'm learning quickly. (Not much choice.)

    I checked out that bike. That's one **** of a big frame. You could fit a 250 in there, by the look of it. Looks pretty old, like a road-bike/MTB hybrid. It should fit 2" tyres or wider though, by the look of it, and suspension shouldn't be hard to fit.

    The down-tube is tilted foward at a fair angle, though, so the motor would have to be primarily mounted to the seat-tube, with a modified mount at the front to compensate for the angle. Not much of a problem. There are plenty available. I like the look of the SBP 'Large' Universal mount, though I didn't use it. I drilled my frame and reinforced.
     
  10. Hajuu

    Hajuu Member

    Last edited: Mar 19, 2010
  11. AussieSteve

    AussieSteve Active Member

    Better than what I did. Because mine's alloy, it's harder to weld, (also no equipment), so I made two 3mm steel curved braces, one for each side of the downtube. Cut from the original engine mount brackets. I just cut off the ends where the 6mm bolt holes were, flattened them a bit to match my frame, then drilled an 8mm hole through the centre. A piece of old tube rubber under each. No problems with cracking or anything yet.

    I've heard some horror stories, though. Al.Fisherman, (Ron), showed me his broken (thin) steel down-tube, caused by drilling.

    My downtube is very large diameter, so an 8mm hole doesn't affect it much. Also, despite the horror stories from drilling, my frame has a hole drilled at the bottom of every tube for water drainage and they don't crack.

    Welded braces should be fine. Simply put a slight curve in a washer and braze or steel weld it on. Job done.

    For Schwinn Cruisers, check out our US friends' builds.
    $200+ here, but about $100 there - the price we pay for living in a nicer place.
    (Now the sky will fall on my head.)
     
    Last edited: Mar 19, 2010
  12. Hajuu

    Hajuu Member

    Haha, nice one.
     
  13. Hajuu

    Hajuu Member

    The second build has begun!

    Found a beautiful condition aluminium frame on the roadside pickup (large rubbish collection in australia).

    Fitted my the same wheels

    Tuned the um 'y' suspension brakes and the gears (my old bike had dodgy caliper breaks and NO WORKING GEARS)

    Removed the engine and handlebar twistshift/killswitch and clutch levers, freeing the engine entirely from the bike, then removed the exhaust - it was nearly entirely clogged. Cleaned everything up as best I could.

    Now I have a complete, working, perfectly tuned mountainbike with a much better riding position, and probably half the weight.

    The only obvious difference in the builds I can think of is because of the aluminium rather than steel frames, I'll have to Add some rubber onto the mounts. I was thinking of trying to use some old tires themselves, rather than just the inner tube, which to me seems like it'd still basically just transfer the vibrations directly into the frame, unlike the notched, studded tire outer.

    Thoughts?

    I'll post some decent pictures after I go back out to work on it tonight.
     
  14. Hajuu

    Hajuu Member

    Hmm. Okay,

    Rebuilt the entire system onto the new frame/bike.

    Still encountering the exact same problem! Basically I started out rolling and started it, ran beautifully, but I wanted to see if the same issue was still there, so I slowed right down, and sure enough, the bike started to kind of splutter and shudder.

    I stopped entirely to check it out and it promptly stalled, then refused to restart (sucking air into the intake but no ignition)..

    Now suddenly it wont start at all again.

    The engine was entirely cleaned, placed onto a new frame, with a new spark plug, and as I say it DID run perfectly for a few seconds.

    Sigh!

    Any ideas appreciated.
    Hajuu
     
  15. Hajuu

    Hajuu Member

    Hm, ok update:

    The other day, we had a storm so severe it was called a 'natural disaster' (our roof at work even caved in while I was working!). This came on in about 20 minutes and passed in about 2 hours, while I was at work, so I couldn't do anything. Prior it was sunny and fine.

    Now, both the fuel and the bike were at the very least outside, at the very worst, the fuel cap wasn't properly on, or the engine was directly in the rain.

    My question is, does this seem symptomatic of water in the; fuel, carb, cylanders or gas tank? And if so, which is most likely, and how do I fix this?

    Hmmm

    Mike.
     
  16. AussieSteve

    AussieSteve Active Member

    Mike, regarding the fuel tank, pull the hose off the carb and run some fuel from the tank into a clear jar/glass. Any water will be at the bottom of the tank and evident in the jar.

    Pull the carb off and clean it.

    Fuel can won't have water in it, unless you left the cap off or loose.

    Cylinder etc won't have water in it.

    Most likely thing, if the water caused your problem, is the electrics.
    Have you tested for spark yet? That should be first, then, if there's no spark:-
    First pull off the magneto cover and check for moisture. A hair dryer or leaving it in the sun should dry that out, unless there's damage, but there shouldn't be.

    Water/moisture around your wire joints to the CDI etc could also be the cause. Ensure that everything is well dried out and try again.
     
  17. Hajuu

    Hajuu Member

    Oh my god! Thank you so much Steve!!

    I cleaned the carb again even though it seemed ok, replaced the fuel with new fuel with a much lower um, volume to lubrication ratio or whatever (it was homelite exact mix + a small amount of caltex 2 stroke oil).

    Let me just say, the thing is running like a FREAKING BANSHEE. Between the new build where I cleaned everything, the new frame, the engine becomming broken in, and the new fuel mix, it's rediculously more powerful than anything i've experienced thusfar.

    Only two issues remain now;

    1. the clear fuel overflow line or whatever comming from the carb (we've discussed this before) is literally LEAKING fuel, not in drops, as a stream. I think we agreed last time that pretty much the only thing that could cause this since my float was ok was that the float tang needed adjusting?

    Just confusing because before it only used to happen on like downwards slopes, now it seems nearly constant.

    and 2. I'm no longer using any chain tensioner on this new build as, quite frankly it was the absolute bane of my existence on the last build, and seemed cheap and unnecessarily resistive/restrictive.

    Anyway, this is working great, except that theres about half a link of slack on the chain, and its too much. I've tried moving the wheel back further but for some reason I can't see the wheel axle wont move back even though there is hanger track left.

    Is there any available solution to such a problem?

    Other than that, woohoo! Also: rubber (I used double) under your engine mount is FANTASTIC. It doesn't really remove any vibration, just kinda dulls it down from being sharp shocks in time with the engine firing.

    Under the gas tank is also very handy as it allows the tank to really hug that frame, allowing for a snug fit that wont slip - ever.
     
  18. AussieSteve

    AussieSteve Active Member

    Can't help with the carb problem, except to suggest a few firm taps on the side with a screwdriver handle. Sometimes, that will help the needle and seat to close properly. Otherwise, float level, but that will only have changed if you bent the tangs while it was apart. Also ensure that the float isn't punctured and that it's moving up and down freely.

    Sounds like you still need the chain tensioner. Have you tried a half-link? SBP sell them - not sure who else.

    Finally, Happy Birthday.
    Have a good one.
     
  19. KiM

    KiM Banned

    Where in Perth are you? THe storm didn't hit as hard in the hills
    only wind and rain no golf ball size hail thankfully, i shut the door and turned the stereo up a lil louder and forgotz about it haha

    KiM
     
  20. motorpsycho

    motorpsycho Active Member

    on the issue with fuel coming out of the carb. overflow tube...
    sometimes when you jostle around these engines, the float itself will get cocked a little bit, so it is not sitting in the float bowl flat. if the float is a little tilted, it will allow the needle & seat to stay open even tho the float bowl is full of fuel. fuel will them come out of the overflow tube.
    I have had this happen with 2 of these engines and a few taps on the side of the float bowl with a plastic handled screw driver usually knocks the float back into position.
    if it was not doing this before, then your float level (the tangs) should not need to be re-bent to adjust the float. run the engine with the gas turned off so the float bowl can empty, and then tap on the bowl. don't run it until the engine dies, just run it a little bit to get the fuel level in the float bowl to drop down, so the float will move when you tap on the bowl.
    if you have never seen the float and the needle & seat set up in these carbs, it is very primative. It works, but it is not the best design.
     
    Last edited: Mar 28, 2010
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