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

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.)

Haha, nice one.

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.

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

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.

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.

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.

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.

Hajuu said:

The other day, we had a storm so severe it was called a 'natural disaster'

Click to expand...

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

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.