KDX - Self made gaskets - How ?

[omrik88]

Hello everyone,

I want to make gaskets for a KDX 200 c3-1988.
The gasket kits are sometime expesive and take a long time to order, so maybe with some basic skills and patience i can make them myself.
I will need to improvise because i don't have the punch tools.

Does anyone know the exact thickness for each gasket needed on this bike? (in mm please).
And what gasket materials/paper i will need to buy?

*I heard the copper head gasket can be re-used by heating it?
Thanks very much for your help! :)

 

[helio lucas]

i usually don´t re-use head gasket, if they are available. but, with a propane torch, heat the gasket very carefully and gently to not melt it. it´s a process named anneal and the goal is to soft the copper gasket. use a gasket sealer when fitting the "new" head gasket like permatex copper seal spray.
if the cylinder and head hasn´t been re-surfaced it can be done with great success, just take care to fit everything in the same position...

all the other gaskets i use oil resistant gasket maker paper bought on the auto parts store. i have a range from 0,25mm to 1,6 mm thick. bear in mind that when the gasket is being tight, it reduces his thick by 15% to 25% depending on original thickness and material, as well as gasket area and torque of the studs.

round, low quality punches can be bought for almost nothing and i use them for cutting holes, mainly for studs... but really is not needed.

i cut the paper using a scissor, x-acto (very sharped knife) when needed. the main cut, i do it putting the paper above the surface to seal, with a rod (i use a 13mm and 8mm ring, closed end wrench) beat gently the paper on the corner of the surface and it will cut the paper just like a oem gasket.
with time and experience the gaskets can be made fast and with a very precise fit. with 0.50mm paper i can do a base gasket in 1 minute.

hope it helps :cool:

 

[helio lucas]

Does anyone know the exact thickness for each gasket needed on this bike? (in mm please).

sorry, i cannot help you with that. but most oem paper gasket are 0.5mm thick.

 

[motopsycho87]

The best way to make paper gaskets is to tape the gasket paper to the piece, then using a small ball pein hammer, tap around all the edges and bolt holes until you have a nice perfect gasket.

Most paper gaskets it doesn't really matter about the thickness of material, or if you even use them, you can always just get a tube of instant-gasket, apply a VERY THIN (too much and it will squeeze out of the edges and block oil/coolant ways) bead of instant gasket around the edge, leave to set for 5 minutes (or however instructed on the tube) then assembly and tighten (never over-tighten)

 

[omrik88]

Thanks very much for your help guys!!!
I know any sort of gasket paper and any thickness can be used, but i really want to do it right once,instead of doing it again. I heard that especially for places where there are moving parts it's very important to put the correct gasket on.
*So if anyone knows the exact thickness for the gaskets on the KDX200-c3-1988
please let me know :)
*About the head copper gasket, i opened the top once and closed the engine, without heating the gasket, and i didn't have any problems. Should i heat the gasket every time i open the top end? Do you know how many degrees it's needed to be heated up to?(celcius - i have a special oven) And i heard it needs to be cooled down fast?
Thanks!

 

[motopsycho87]

Normall with copper a blowtorch does enough, I would expect the oven to need to be around 800c, general concensus for normalising metal is roughly 80% of melting temperature.

I have an E model gasket set right by me if you want me to measure the thickness of any gaskets in particular

 

[helio lucas]

I heard that especially for places where there are moving parts it's very important to put the correct gasket on.

sometimes thickness just don´t matter, like a powervalve cover or clutch cover.
most places is important. base cylinder gasket alter port timings and compression, head gasket alters the compression. some engine cases have a gasket instead on non drying sealant, not your case but, that gasket thickness is critical.
and the list goes on :cool:

 

[motopsycho87]

Reed valve makes a dinky little difference also, I removed mine and just use silicone

 

[julien_d]

Reed valve makes a dinky little difference also, I removed mine and just use silicone

Right, that's what engineers do.

:blah:

 

[glad2ride]

Some clutch covers and side covers have parts that fit to the inside of them, so be careful of just using any old thickness.

Don't use silicone. If you really need to use silicone, take up a cheaper hobby.

 

[motopsycho87]

Right, that's what engineers do.

:blah:

Ok, so the carb I've fitted has been boasted by Keihin to have a shorter gap between the venturi and inlet of the bike for better throttle response, because the air/fuel mix has less distance to travel. So bringing the reed cage 1mm closer to the engine by removing the gasket, on top of the carb being 16mm shorter creates a much greater throttle response. And before you mention, I know adjusting carb to engine clearance requires porting adjustment and exhaust adjustments, I'm working on that. Also, just to add to your ammunition, I am a fully qualified light vehicle mechanic, have passed my level 2 in basic engineering operations and will be studying advanced mechanical engineering the next 2 years. You really are entitled to your opinion, but please don't try and turn every bloody topic into a slagging match. I know you thrive off of my retaliations and I am a fool to keep biting back. What do you want me to do next? Post my certificates and resume up for you to scrutinise?

I will give you one thing though, the bike was running like crap, having not ridden a well sorted KDX or even seen one to compare it to, I had no idea how badly it was running, turns out one of the exhaust valves was snapped (of which I have made a replacement pair) and the centre valve was out of time, that plus the nikasil coating had almost completely worn away and had a huge gauge in it from where the previous piston (yes the previous owner replaced the piston without a replate) had chewed the circlip into the cylinder wall. I can't wait to get her running properly after the replate.

Silicone is better than gaskets if you know how to use it right (i.e. not blob it), you eliminate a possible variable (crushed thickness of gasket) thus allowing you to create tighter tolerances. I would lap the surfaces together instead but I really cant be arsed.

I have a whole gasket set staring me in the face right now, I choose to use RTV sealant on specific parts where they pose a benefit.

 

[helio lucas]

watch out for some rtv sealants because most of them are not gasoline resistant and start to break down with time allowing for a air leak. most are only oil resistant :nod:

the gasket taken out from the reed-valve-to-cylinder-joint may indeed have some effect on engine, not from carb venturi being 1mm closer to crankcase, i believe, but from a increase in crankcase compression.

anyway, a thinner gasket coated with gas resistant sealer is the way to go. permatex have some very good products for the job.

 

[julien_d]

Easy man. I just think some of the things you come up with are too good to pass up a jab at. You have frankenbiked that thing you are messing with to the point that I doubt it will ever run worth a crap. Again, just my opinion, take it as you will. Best of luck, as always... Messing around with stuff is certainly the best way to learn how different things affect overall performance.

Very impressed with the valves you made. Looks like top notch work. If you were able to pump those out, you could make a buck selling them for sure.

 

[whenfoxforks-ruled]

Throw out all them damn torque spacers!

 

[Ol'89r]

omrik88
In regard to annealing a solid copper head gasket. Use a torch with a large tip, not an oven. Heat the gasket in a circular motion being careful not to heat any one spot more than another. Heat it until it turns a dull red in color then drop it into a bucket of water. Use Copper-Coat spray for a head gasket sealer.

 

[motopsycho87]

Dropping copper in cold water from red hot has no benefit whatsoever other than cleaning it. It only affects metals with a high carbon content in which quickly cooling hardens the metal further. In which most processes that involve quenching metal after heating use an oil bath as water cools too rapidly and can create stress fractures :)

 

[Ol'89r]

Dropping copper in cold water from red hot has no benefit whatsoever other than cleaning it. It only affects metals with a high carbon content in which quickly cooling hardens the metal further. In which most processes that involve quenching metal after heating use an oil bath as water cools too rapidly and can create stress fractures :)

Well. I guess I have been doing it wrong for the past 45 years. :ohmy: I should know better than to come into the KDX forum. :bang:

 

[motopsycho87]

I'm not saying that, it's common practise to water quench PURE copper because it is so soft it doesn't fracture and you get the benefit of clean metal. Though on thinner copper you may suffer distortion.

I work in a specialist foundry that produces copper based alloys for the aerospace industry, literally every day I am heat treating metals to attain certain hardness characteristics, copper can only be softened by heating, fast cooling has no effect. Also, when trying to soften a high carbon metal, air cooling is preferred, the quicker you cool, the harder it becomes.

Bit of bedtime reading if, just like everybody else you believe I am full of ****, http://www.wisetool.com/designation/treatment.htm

Apologies for the tone, but I really enjoy engineering, metallurgy and engines, and work within the field, it really gets my back up when people say "ive been doing it wrong for the past 1000 years, but because ive been doing it longer, im right", no, its just shows how ignorant people are.

 

[Ol'89r]

I'm not saying that, it's common practise to water quench PURE copper because it is so soft it doesn't fracture and you get the benefit of clean metal.

I work in a specialist foundry that produces copper based alloys for the aerospace industry, literally every day I am heat treating metals to attain certain hardness characteristics,

its just shows how ignorant people are.

motopsycho. No need to get all upset buddy. I was just answering omrik88's question about heating copper head gaskets. If you work in a foundry you obviously know what you are talking about.

This is a method that was taught to me by a very famous engine builder many years ago. Don't know all the technical crap about it, I only know it works. Never had one leaky head gasket using that method. Just passing that info along to omrik88 and anyone else that wants to hear it. Didn't mean to step in the middle of your $hit storm.
Sorry for being so ignorant.

 

[motopsycho87]

The ignorant part wasn't aimed towards you atall, it just always seems to be the common tone along forums, so I really do apologise for adding it in there!

 

[whenfoxforks-ruled]

The 25 dollar full sets of gaskets are looking cheaper by the second.

 

[motopsycho87]

i paid £40 for mine, uk is a complete rip off.

 

[jsantapau]

The 25 dollar full sets of gaskets are looking cheaper by the second.

now that right there is funny

 

[omrik88]

Thanks alot for all the information !

About the copper gasket - i hope that heating it will not change it's thickness. If i can't get a copper spray is there something else, or just use the gasket like that?

*About the exact thickness again of all the other gaskets on the bike and materials to use - can anyone be more accurate?
I'm a bit confused about this.
Thanks :)

 

[whenfoxforks-ruled]

If there is a gasket between your tranny cases, a few thousandths of an inch could destroy the gears/not shift. The left cover could hit the rotor if too tight, probably not. Do not cover the vent. The right cover holds the shift lever in place, it may take some clearance, maybe not. The base gasket is crucial for port timing. There is no way I have ever heard of making the head gasket thicker. Metal has memory, to some degree. Literally. Tapping a gasket out on a steel or iron engine part is 1 matter. A magnesium or aluminum part is just dumb, and potentially much more than the gasket set, imo. Copper spray is readily available from auto and motorcycle shops, maybe not the local head hunter at the beginning of the Amazon River?