KDXRIDER.NET

hi all just joined i'm from lancashire in the uk .i have just bought a kdx420 originally from the US that needs restoring.i'm more of a roadie than an off roadie got a z1 currently restoring,z1a thats done,gpz1100b2 done,katana 1000 needs doing,cbx1000 in boxes,cb750k0 done,rd350lc needs doing ,bmw g650 gs (pants really).back in the day 35 yrs ago ha had a rm125(totally unreliable) ,dt175(cracking bike) rings went on it still got me home. so has u have gathered i'm a bit of a novice again.so really looking forward to learning from you guys and probably going to need a lot of help.i'm an engineer so not frightened about restoring it really but i know parts are pretty hard to find.1st question is what is the afternmarket silencer on it cos the cap has no holes in it apart from the screwed rod in the middle and it blows out around the outside kind of where the fins are.had to see if it runs it fired up with a remote fuel bottle pretty quickly but died pretty quickly throttle cable all over the place.then it was a bugger to start .eventually it did kept revs up a bit smoked me out .blowing at front of exhaust at the header and there was black residue like oil comin from there and out of muffler is that crank seals.heres some pics when i bought it.going to need lights etc that will be fun.if you spot anything wrong be grateful for the heads up.
cheers guys

Welcome to kdxrider.net. Thanks for signing up and getting involved.

Here's a link with the parts diagrams. You can click on the part number to see which other models came with that exact same part.

That is not the stock spark arrestor. As an example of the handiness of the diagrams in the link:

Yep thanks cmnsl do the schematics as well i think they are in holland wot are ur thoughts on the black residue is it because it took ages to get it started again poss flooded or more like crank seals did feel oily.

A lot of neglected bikes show that. Some with just incorrect jetting do it also. I think it is a bit early to jump to checking the difficult to check things before the easy to check things. How's the air filter, plug, reeds?

So the silencer on that bike is a Supertrap, they were big in the 80s. You could adjust your back pressure by changing the number of baffle plates on the end (it was a gimmicky marketing campaign). The black oily residue coming out is the remnants of old pre mix, or "spooge" as it is affectionately known in the 2T world.
Looks as though all the big parts are there, including plastics and tank, so that will help. First order of business should be to tear down and clean the carb, noting the needle and jet sizes/positions. New filter, check reeds and all gaskets. New springs and gaskets for the exhaust. The Supertrapp can be cleaned by removing the end plate and all baffles. Compression and leak down checks should be high on the list as well. Looks to be a fun project. Any idea how it ended up in the UK?

Yep dkmotorcycles over here imported it they swept and still sweeping through california i think brought thousands of bikes since the classic scene exploded a few yrs ago. Might be a stupid question how do you do a compression test on this keep booting it over cos obviously on my bikes i turn it over on the battery but they turn over a few times to read true compression and please enlighten me on leak down test on 2t. Already got some good info thanks guys

Compression test pull the plug, insert gauge and cycle the kickstarter by hand a half dozen times. Leak down will check your overall crank seal health, involves pulling the pipe and carb and plugging those holes, place the piston at BDC and pump up to 6 psi (don't go over 8 or you can induce a seal failure). Leak rate should not exceed 1 psi per minute.

Thanks for that great info on leak down test

I've always done the compression test with WO throttle and rapid full kicks until pressure doesn't climb any further, engine cold. I was taught no matter what, always use the same procedure so you can compare to past readings. Each his own I'm sure.

thanks for that waiting for a workshop manual at mo but goin to do all these checks before i strip it

bufftester wrote: 05:30 pm Jan 11 2020 Compression test pull the plug, insert gauge and cycle the kickstarter by hand a half dozen times. Leak down will check your overall crank seal health, involves pulling the pipe and carb and plugging those holes, place the piston at BDC and pump up to 6 psi (don't go over 8 or you can induce a seal failure). Leak rate should not exceed 1 psi per minute.

What do you guys like to use to plug the exhaust and intake? I’m curious. Plumbing parts from Lowe’s maybe?

I have two big rubber plugs (like they use on test tubes, etc) that I found at a swap meet of all places. One of them I drilled a hole and tapped a shcrader valve in for pumping with a bike hand pump, it gets held in the carb boot by the clamp, for the exhaust I shove it in and hold it in with some safety wire run between the 2 spring mount holes. You're only going up to 6 PSI so it doesn't take a lot to hold it in place

sounds like a great idea and a cheaper option

Y’all got me inspired to finally check the compression (+ I had the tank off). Like I shoulda done before I plunked down my cash.

Happy day. Bacardi & KDX get the same fire power rating.

No wonder I can’t kill this thing with my lack of fine tuning skills. Some nice PO musta been in there not too long ago.