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Discussion Starter #1 (Edited)
Original thread here of buying a junk bike: Click

Well ive kinda gone off the deep end and am now going all the way with this build.

This wont be the most extravagant or high end build, but for me and the kids its great. (Also fixing up an LT A50 and have other LTZ) Lucky enough to have my own trails.

Doing this because I like this forum, I love the LTZ400 models in general. Figured this would be a single place I can ask a million questions instead of starting separate threads.

Current progress:

Stripped, gusseted and powder coated frame - Newer sub frame
Dual Piston front brakes from YFZ450 (complete setup to come)
Alba +3 a arms and +2 steering stem
Alba front bumper
All the boring stuff like bearings and pads etc







What I have on hand:
SS brake lines
Tusk Axle
Factory length Fireball racing swingarm with TM double roller guide
DID X ring chain, new sprockets
All the yfz450 brake stuff, gonna do the rear dual piston caliper too.
FCR 39 slant
Ebay powerbomb - undecided muffler but I have good old ones
Factory rear shock re valved dual rate
Alba beadlock and 6 ply china tires

Unfortunately oem shocks for now until I find a good deal
 

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Discussion Starter #2 (Edited)
Couple hang ups so far but not too bad.
Thought I was going to live with the stock motor and be happy with it. Literally today my swingarm bushings came in and am ready to progress with the rear swingarm/axle etc.

When.....this this pops up for $250 today.

What appears to be a MX FCR 39 (After I trolled ebay forever to finally get a slant for $200 lol)


Hinson - I hope that its all in there. He claimed its the full kit and showed me a site where it was $1100+ new!





Here is the story with this (his story). Guy buys this used already setup with "maxpower sleeved 450 stroker" and stage 2 hot cams with hinson full clutch and basket set.
They claimed to have check all valve clearance and timing, but when they put it all back together discovered that likely the rings are bad.

The thing smokes pretty bad, what looks white but smells like oil burning.

He didnt want to tear it back apart and pay the guy to keep fixing so he just wants it gone.


So I figured for that kinda money, maybe it would be worth going thru the motor to have it in my new build. The guy had a couple pictures of when they had the motor open.
I can obviously see maxpower 96mm on the piston. He also showed proof of a "Cometic" head gasket they used. Said he had a hard time finding one.

Do these pics confirm anything?





I got it to fire and rode it around so I guess the motor is not real bad yet. Didnt run great tho, but I suspect mostly due to the carb jetting and it still had the crappy oem petcock with open vac line.
Well that is where we are at. I hope im putting enough effort in for you veterans to help a noob like me! I will definitely be needing some help thru the motor.
 

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I think it is what he says it is, but what's with the clutch cover? Is that a DRZ engine? The LT-Z never had a clutch access cover.

That's a stealth big bore cylinder from Max power. They don't use the set screws anymore though. I would look that thing over for cracks in the bore, if there's unexplained oil consumption.


Those are the old style hotcams that most people loved. They have changed them for the worse since. Those old style cams are great for XC/MX/trail type useage. They do great low to mid but are a little flat at high rpm in a big bore.
 

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Discussion Starter #4
Good eye CFM. That may explain the unmodded carb and intake boot, maybe original. Also, the headstay brace is gone....seems there is always that interference with DRZ boot and the LTZ



Slapped a 660 petcock on it fired right up. The motor seems strong, but boy is it smoking.


 

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Does it have reverse? That would be a way to tell if it's from a DRZ. It may also just have a modified clutch cover, which is real hard to come by now
 

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Discussion Starter #6 (Edited)
Does it have reverse? That would be a way to tell if it's from a DRZ. It may also just have a modified clutch cover, which is real hard to come by now
It does have reverse on bar hot start lever. Looked over my stock Z everything looks the same otherwise (to my caveman eye).

Very interested to know about this clutch setup. Edit: I looked it over and its gotta be a modified oem LTZ cover.




Looked over the head and stuff, didnt see any glaring issue. At least on the outside. No oil spots overnight too.
 

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Discussion Starter #7
Started tearing apart the yellow one. Drained the oil, a little "silvery" and way overfilled.



Unfortunately found cracked case :(


 

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Ouch!
 

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Unfortunately, I’m fairly sure the cases are a pair. This usually means a junk bottom end unless you want to try JB Weld or having it welded. I haven’t seen many say it worked, though.
 

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Discussion Starter #11 (Edited)
Looks like someone already tried that LOL





Man, this poor bike.

So looks like ill be counting my loses here. Now im thinking sacrifice the parts from this motor and install on my stocker thats in the frame. Any tips would be awesome.

Not sure that it means anything, but the back of the valves in this cracked motor look new compared to the backs of my stocker motor. Hopefully there are some good parts in this thing.
 

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Discussion Starter #12 (Edited)
Got the motor just about ready to come out.

Peeled the top real quick. Luckily it looks like the same parts from the pics he showed, so thats a plus.

Now, ive got this motor with fancy parts....a stocker over there.....what next? Hopefully I can bolt the top end, cams and clutch on my good motor.

Any advice on piston rings and gasket kits that I need id appreciate the help! Im seeing gasket sets on feebay for cheap and Cometic 96mm gaskets available....but I need rings.



I have the new cometic base gasket I got with the bike. If the Cometic head gasket that they recently put on is still good, can I re use it?





ANY advice or info on any of this is greatly appreciated!
 

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I’d never re-use a head gasket, just asking for trouble. The Cometic gaskets will work fine. You’ll have to see what piston you have to order rings. Probably send them a picture of your piston to get the correct rings for it. Once you get them, you’ll have to file the ring gaps down to spec when installing them.
 

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Discussion Starter #14 (Edited)
Understood on the head gasket, thanks bro.



Got an email back today from Maxpower

From the pictures it apears to be an Ice Cube with no copper compression ring, on top of the cylinder. It looks like someone has put screws in the cylinder to hold sleeve in place, we do not do this procedure. If it is holding up, all the better.
 

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Understood on the head gasket, thanks bro.



Got an email back today from Maxpower

From the pictures it apears to be an Ice Cube with no copper compression ring, on top of the cylinder. It looks like someone has put screws in the cylinder to hold sleeve in place, we do not do this procedure. If it is holding up, all the better.
I'm using second hand info here, but I was under the impression that they did use the set screws at one point in time, then abandoned that method for a tighter interference fit later on. I believe I even got that out of one of the guys from Max Power.

I also know that since then, they have been o-ringing the top deck, which is a groove cut into the top deck, around the cylinder, where you lay a piece of wire, butting the ends. This wire sticks above the deck surface, and tightens the seal at the head gasket when you bolt it together. I am a big fan of that. I do the same on my big bore builds. I'm not sure it can be done with those set screws in there though. I believe at that time, they were just using an appropriately sized head gasket.

I would lightly deck the deck surface of the head and cylinder, to check for any low spots. 1, because sleeves can bring about abnormal issues, and 2 because just about every head that I do this to, had a low spot, and just about every time I have anything like this come in with a head gasket issue, there are low spots in the head causing it. Some were even chronic issues that had already had the head gasket changed a couple times trying to solve the issue. By decking, I always solve it.

Personally, I do what they call lapping, to the deck surfaces. I have a flat plate of glass, that I spray adhesive down, and stick sand paper to. Then I do figure 8's with it, and look for any area that is not showing contact. That would be a low spot, and I will keep going until it's gone. Keep in mind that finish matters. I generally use 320 grit to finish. I use something coarser at first if I have a ways to go to. This is a nice way to only take what's necessary. If you are unsure about your finish, you can spray the gasket with copper coat. The MLS style gaskets are fussy on finish. It's not a polished finish that they want, but it's not too far from it.
 

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Discussion Starter #16 (Edited)
Thank you! Reply in quote below.

I'm using second hand info here, but I was under the impression that they did use the set screws at one point in time, then abandoned that method for a tighter interference fit later on. I believe I even got that out of one of the guys from Max Power.

I also know that since then, they have been o-ringing the top deck, which is a groove cut into the top deck, around the cylinder, where you lay a piece of wire, butting the ends. This wire sticks above the deck surface, and tightens the seal at the head gasket when you bolt it together. I am a big fan of that. I do the same on my big bore builds. I'm not sure it can be done with those set screws in there though. I believe at that time, they were just using an appropriately sized head gasket.

Im sol on this one, stuck with what ive got. The o ring does sound superior.

I would lightly deck the deck surface of the head and cylinder, to check for any low spots. 1, because sleeves can bring about abnormal issues, and 2 because just about every head that I do this to, had a low spot, and just about every time I have anything like this come in with a head gasket issue, there are low spots in the head causing it. Some were even chronic issues that had already had the head gasket changed a couple times trying to solve the issue. By decking, I always solve it.

Im going to assume the worst and agree that this is probably a chronic issue they couldn't fix.

Personally, I do what they call lapping, to the deck surfaces. I have a flat plate of glass, that I spray adhesive down, and stick sand paper to. Then I do figure 8's with it, and look for any area that is not showing contact. That would be a low spot, and I will keep going until it's gone. Keep in mind that finish matters. I generally use 320 grit to finish. I use something coarser at first if I have a ways to go to. This is a nice way to only take what's necessary. If you are unsure about your finish, you can spray the gasket with copper coat. The MLS style gaskets are fussy on finish. It's not a polished finish that they want, but it's not too far from it.

This makes complete sense to me and I have a big thick flat sheet of glass ready. What grit would you suggest starting just to check if there are low spots? Or say what the heaviest grit you would go first?

Ill start tearing it down soon and post some pics. What have I got myself in to:surprise:
 

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Thank you! Reply in quote below.




Ill start tearing it down soon and post some pics. What have I got myself in to:surprise:

I have gone as far as 60 grit, I generally stay 80 or finer. If you go too coarse, you can find yourself trying to get past the deep scratches left by the coarse paper. I always finish with something around 330.

You want to be careful of your choice of adhesive also. It needs to be very thin.
 

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Discussion Starter #18 (Edited)
Roger that CFM.

Making my way thru disassembly.

Please let me know if im looking for any specific damage. Or if there is something you want to see.


valves are crusty.


At least the parts were really in there!










After a closer look. The last "corrugated" piston ring is missing a large piece of it and looks like its interlocked in another part. Might be hard to see. Im gonna say this would cause the smoke?







Now where are gettin somewhere?? :) What now?
 

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Discussion Starter #19 (Edited)
Ok got a little further. Found major milky situation. The water pump impeller was really stuck in there and maybe not working....would this cause the milk issue as shown?
(was not leaking out the weep hole, ive dealt with that before)








Thank you guys for all the help, despite all the issues im having fun learning and documenting for others to learn from.
 

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Someone put a few bucks into that one. The ring that you are missing part of is the oil flinger. Doesn’t make a seal, it’s just there to help throw oil on the cylinder walls. Probably not your smoke issue, but needs to be replaced.

That corrosion all over the water pump shaft made the inner o-ring fail, allowing coolant into the oil. As with any seal, it needs a smooth surface to run on in order to do its job.

With all that going on, you’ll want to pull that brown plastic gear and the oil pump. I’d replace the plastic on no matter what shape it’s in. It runs the oil pump and will shear off the teeth if the oil pump got any junk in it. The fact that it hasn’t means it wasn’t run very long with milky oil. Also take oil pump apart and clean it out/look for wear.

Those look like aftermarket valves, probably Kibblewhite. Can’t see the springs to tell if they are factory, but I doubt they are. The two intake valves look nasty. If they are wet with oil on the other side (down the intake ports), the those valve seals could be your smoking problem. Either that, worn rings, or blown head gasket.
 
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