Four stroke options

[FourstrokeForever]

Seems like you're hard at it James. Nearly ready for a test ride already!

What swing arm are you using? If you move the top shock mounts, chances are that someone will complain if you use the bike for a national competition.

To get the ride height you want.....remove the shocks and then the shock springs. Set the bike on an adjustable jack with the height dictated by your known ground clearance measurement. (While speaking of ground clearance, it would be best practice to have at least 25mm or so to spare before the frame bottoms out to the dirt).
Re-install one shock without spring to the frame mount only. Now raise the rear wheel/swing arm to the travel amount you have figured will work. Next, compress the shock to the stop and then it's a just a matter of finding where the shock needs to be mounted onto the swing arm. Make a mark on the swing arm and let the back wheel back to the ground. Confirm that the new shock position will allow full travel by lining the lower shock eye up with the mark on the swingarm. If that's all good, try clamping the shock to the mark with a G clamp or similar and then test the wheel travel. Now that you know you have found where the shock needs to be mounted, make up some mounts for the swingarm 

[LWC82PE]

If the forks are 35mm they are not PE. Assuming they are suzuki and leading axle they could either be most likely 79 TS250N, 79-81 RM100 or early 80's DR250S. Post a photo of them if you want positive ID.

[LWC82PE]

As far as suspension goes,what part of the bike should bottom out first when your setting one up like this?The

Well I would think you want the use all of your shockabsorber stroke first and have the shock being the limit of the travel. You do not want the tyre hitting the frame/fender/airbox etc all the time and have that being your ‘limit of travel’ or 'bump stop' . Its the same thing if your front tyre hits the lower triple clamp when you still have a few inches of fork travel t go. If your tyre is hitting something and effectively being the limit of the travel, it means you need to reduce the travel. From my experience most of your extra gained travel is going to come from below the horizonatal line of the sprocket-pivot-axle due to angling the swingarm down more but the compressed length of the shocks is also going to be a determining factor aswell. To get the best end result you really need to work out shock mount positioning and shock length/stroke all together at the same time otherwise you may have a compromise. It depends on how important it is to you to get the maximum travel possible.

[James Lee]

My calculations[guessing here]tells me when I extend the swing arm and leave all the shock mounts stock,these shocks will be the correct stroke and length,Im hoping anyway.
I fired it up today for the first time and it sounded great.Im using PWK carb,it squeezed into the manifold nicely and sounds awesome,very responsive.
Fitting a new/old stillmoto front guard and an MSC rear but have to paint them,rm125 seat and tank seem to fit great..
Ill work out how to post pics when I get the guards etc mounted properly.
Im very close to testing now.

[James Lee]

Anyone else building a 4 stroke VMX bike?I love to hear and see it.Im looking for my next build already.

[FourstrokeForever]

That was quick....How about some photos

[James Lee]

Here it is,far from finished but together enough to test ride and make sure the box is OK.

[LWC82PE]

Well that looks a lot better than stock i think. From what i am seeing here, the forks are 78/79 PE175-250.

[James Lee]

Thanks LWC,the forks have some bad rust just above the seals so Ill be on the hunt for some decent ones to rebuild.
Im looking forward to tearing it down and cleaning/painting it all.
The ola inspired alloy side panels didnt turn out as I envisioned.Ill probably ditch them for some oval plastic ones.
Will report back tonight with some action pics if all goes to plan.

[shelpi]

good work, looks the goods

[FourstrokeForever]

Cool. Another fourstroke MX'er back from the dead.

[James Lee]

And what an awsome 4 stroke MX bike it is.On my mates tight natural terrain track this thing out corners anything Ive ridden out there.I think the PWK carb is way too big as is splutters everywhere but wide open and just when the power comes on it farts  but pulls really strong down low.I somehow lost the main jet for the original carb,can anyone tell me the jet I need?I found one that fits but it wont run right with it.
Got some great action pics Ill post when my mates comes round,there were taken on his flash SLR.

[LWC82PE]

Are you using the stock 25mm offset SP triples or the 30mm offset RM/PE triples? I cant quite fully tell by the distant photo.

[FourstrokeForever]

Good stuff James. It's great when everything you do works as planned. My hotrod XL420 is one of the best cornering bikes I've ridden as well. Funny how bikes leave the factory in an average state of handling when with a few tweaks here and there turn it into great bike...
Have fun with the carby gremlins. Sounds to me it MIGHT be the opposite of what you think in that maybe it needs MORE fuel down low. Try lifting the needle to start with. If that makes it better, also try a larger pilot jet.

[James Lee]

Im just using the stock SP ones,would the 30mm ones be better?Does that mean my front wheel will be 5mm further forward?
Ill try lifting the needle on this carb,will give me an excuse for another test ride.Any chance of a pic of this hotrod XL you speak of?