KawasakiTrax Community
Tech Information => General Help => Topic started by: shizznats on October 19, 2012, 08:39:38 PM
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So with the new forum and all, I'll recap my situation and my recent unfortunate findings in my 81 LTD engine to see if you guys have any advice...
I picked up a 1981 LTD 440 for $100 off craiglist a few months back. It sat outside for about 4 years straight so it needed a lot of work. I took out the motor and got to work on it. First thing I did was remove head and cylinders to inspect everything. There was some gunk and carbon buildup which I cleaned up and then replaced the cylinder base, head, and intake gaskets amongst a few other things. After that, I had some trouble with the carbs but got everything sorted out and last week I had the engine running. I was running on premix since I wasn't sure about oil pump, but did the output test and oil pump checked out. Also put water in the cooling system and confirmed the thermostat opens up water pump works. Everything was going great. That is until I noticed water seeping from the cylinder base gaskets on the exhaust side >..< Today, I took everything apart and couldn't believe what I found... pistons, on the intake side, were scored... the right one actually has a flat spot on it which you can even see in the picture below. Exhaust side looked alright; just some browning. Cylinders have slight scoring... there are a few spots I can feel with my fingernail... again, worse on that right hand side. I have no idea what caused this as I was running on 40:1 premix the whole time I was working on the engine and test running it.
Based on all this, what advice would you guys give me? I'm guessing pistons are beyond saving, but do I need new cylinders as well? Thanks in advance!
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Did you change the crank seals when you had the motor apart? If not, change them.
Being that you had a coolant leak around the base gasket, it would be safe to assume you were also leaking air. This would make it run lean, and could cause this damage.
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Thanks. We did change the crank seals but we didn't do a good job with the cylinder base gaskets so it's our fault they were leaking. At this point, based on what you see in those pictures and what I described, what would be our best option? The cylinders have some scoring that can be felt with a fingernail but I know that since these are chrome plated cylinders, reboring/honing is not possible or very expensive. Can we leave the cylinders as they are and just change the pistons and rings? If we do just put new pistons in there, would it be better to leave the old rings (assuming the end gaps are to spec) since they are seated to the cylinders, or is it better to put new ones? Only reason I ask is with new rings, the cylinders usually have to be honed so the rings seat properly and I'm not sure we can do that...
Any advice is much appreciated. Thanks!
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IMO, at a minimum, change the piston and rings. I have lightly honed chrome cylinders with success.
Don't use any sealant on the base gaskets when you put the motor back together.
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The key here is "lightly honed" If there was decent compression before you pulled it apart, you could get away with it but you might want to start watching for replacement parts..
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carefully use "the works" toilet bowl cleaner to take any aluminum off the walls where its scored and then check for grooves
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Is this like muriatic acid... is it as effective? I've heard of some people using liquid plumber but most say muriatic acid is the way to go
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It has muriatic acid in it.
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I have talked with several snowmobile guys in detail about the cast iron bores that a lot of these LTD's seem to have been fitted with over the years and although it will work for a while cast iron bores and cast iron rings really aren't a good idea in an LTD... From the factory I believe they came with a chrome bores and cast iron rings...
Although others may disagree from what I've been told by people in the business for 20 plus years, you want chrome bore/or nikasil with cast iron rings or a cast iron bore with chrome rings... If anyone has a source for chrome rings for an LTD please post it up as my local supplier is no longer in business and would love a new supplier...
I agree with everything else said, good crank seals are a must and the new ones don't seem to last like the originals did, because the originals had a metal wall while the new ones are plastic. LTD's are very picky about how they get put together... I really don't like the bolted on head, especially reusing bolts many times... I would recommend going and getting some copper washers for the head and follow the torque spec to a T! Re tourquing the head is also a good idea after a heat cycle or two!
If you really want a two stoke to last run an EGT gauge! They're not cheap tho!
Good luck!
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On Invaders, the head and cylinder studs will stretch over time. This can let the acorn style nuts used bottom out and it will appear that they are torqued tight but they are only tight to the top of the studs, and the cylinders are not tight. Adding a thick washer will help this from happening (more room inside the nut)
true about the chrome rings on a steel bore or steel rings on a Nikisil (or chrome) bore.
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Here is the info about ring compatibility. This is from Wiscoe's website.
All Wiseco rings can be used in cast iron, nickel ceramic platings (Nikasil), boron composite, and Electrofusion bores.
CAUTION: Unless otherwise noted, Wiseco rings can NOT be used in chrome plated bores. Engine damage will occur.
*CSM & CDM rings are designed to be used in chrome bores.
CSM: Nodular iron, phosphate coated, internally notched
(for use in • Chrome Bores)
CDM: Nodular iron, phosphate coated, internally notched
(for use in • Chrome Bores)
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Cast iron rings for chrome bores!
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Thanks for the replies! The cylinders turned out to be ok, so I bought these aftermarket pistons/rings and put them in the engine today:
http://www.ebay.com/itm/120817720787?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
Not sure what the rings are made of, but they were black which I thought was interesting. The problem is that I'm only getting 90psi of compression on each cylinder when I should be seeing closer to 120 or 130. Is it normal to see low compression after putting in new pistons/rings before running the engine? (I put plenty of oil on cylinder walls and pistons/rings) Thanks!
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Not sure about the Ebay listing showing John Deere and LTD together. I'n not aware of any John Deere sleds that would use the larger rist pin of the 81-82 LTD? As for compression it should go up after they seat.
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Yes, the title is a bit misleading but I found out that those pistons do indeed have the larger wrist pins. They were identical to the old pistons I pulled out and fit perfectly. The part number is 8072 for these pistons. I believe they are the only aftermarket pistons for the LTD out there.
Good to hear about the compression.. going to start her up in a few days. Is there a certain break in procedure for these engines that I should follow? Thanks!
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I have always tried to vary the speed for the first miles, no constant speeds for an extended length of time. After the first time they get up to temperature, it doesn't hurt to re-torque the heads.
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What is your ring gap and piston clearance in the cylinder? That wil tell a lot of where your compression should be. 90 still sounds low and it's going to start hard. A little oil down the plug holes before you start it will bump it up temprarily to get it to fire for break in.
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When Twister says a little oil down the cylinders, I would add to his comment, one tablespoon through the spark plug holes. 90 psi is going to be hard to get started. The extra oil helps the sealing and temporary bumps the compression up.
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I would strongly recommend you check the leakdown on that engine. If it is less than 5% you need to check the squish clearance . Google it, lots of info on how to do it. My guess is the aftermarket base gaskets or pistons are slightly different than stock. Probably should be around .070 stock. Someone else may know the exact figure. As far as that 90lbs going up... not a chance. You already have oil around the rings that will bump the compression in itself. Breaking in a motor doesn't pick up 40lbs of compression, at least not in my world.
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Are you sure your compression tester is accurate?
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Thank you all... just saw these replies now (I'm a little slow...) Doesn't sound too encouraging for our engine running with the new base gaskets, pistons, and rings :/ ... we're fairly sure the compression tester is accurate and we were getting the same reading on both cylinders (90psi). We are going to try to check the squish clearance and do a leak down test and post those results once we do. Thanks again.
Edit: Would this be the correct procedure for doing a leak down test on this motor?: Remove one spark plug, hook up compressor with a gauge in it's place, plug up the exhaust and intake ports, put piston at TDC, block the clutch so the piston can't move, apply approx. 100psi, and watch the gauge for about 20-30 min? Repeat with other cylinder. I read about this a while ago but want to make sure I'm remembering correctly.
Also... would a leak down test even be useful at this point... we know that the new pistons/rings have not seated yet so wouldn't we expect there to be too much leak down until we run the motor and they (hopefully) seat?
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That will work. All it is going to tell you is if you have leakage past the rings or a head gasket leaking.
Oil in the spark plug hole will tell you the same thing, add oil, if the compression goes up. it's the rings. If it doesn't, it's head gasket.
A leakdown test will show more on a 4 cycle motor, like which valve is leaking. Since a 2 cycle Kawi motor doesn't use valves, why bother with a leakdown test.. (just my opinion)
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Do a leakdown test for a two stroke engine.
Plug exhaust and intake, leave spakplugs in, apply 10 lbs of air pressure to the impulse fitting.
If it doesn't hold pressure FINd the leak.
Google 2-Stroke leakdown test or crankase pressure test.
Not doing this will result in engine failure. BTDT
Lloyd
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From what I understand, a crankcase pressure test and a leakdown test are two completely different things that get confused a lot. We did a crankcase pressure test, found that the MAG side crank seal was bad, replaced it, and re-ran the test... motor held 7psi of pressure for 10 minutes so we were satisfied. A leakdown test might be more appropriate to check if air is getting past the rings.
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Alright so I just went to check the compression again and here is what I got:
Cyl 1: 90psi before adding oil, 110psi after adding a tbsp of oil through spark plug hole
Cyl 2: 90psi before adding oil, 100psi after adding a tbsp of oil through spark plug hole
Idk if it matters, but it took quite a few pulls to get the readings above, not just 3 or 4. Again, this motor has not been started since the top end was rebuilt so we're hoping that the rings will seat and it will bump our compression to what it should be (120-130?) Possible based on the above?
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This is just my opinion but compression of 110 psi on each side or above should be fine.
125-130 would be good bur 110 or above should work.
Lloyd
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Just curious did you use a flex hone to cut a fresh cross hatch (lightly) prior to reassembly? Joel
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Just curious did you use a flex hone to cut a fresh cross hatch (lightly) prior to reassembly? Joel
We did a lot of reading about this... there are some who say to lightly hone nikasil plated cylinders and others who say not to come within 10 miles of them with a hone, and that they will seat without any cross hatching. After reading a lot of articles and threads on the topic, I decided that since I have no experience with honing cylinders, I'll leave them be. I simply put some muriatic acid to get some aluminum residue off of a few spots on the cylinders, and then cleaned them and reassembled.
What do you guys think... should these be honed prior to break in?
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I know it's debateable...But I have honed several chrome cylinders lightly without issue.
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Did you use OEM pistons? If you did not then like That Girl Racing said, "check the squish clearance". If you still have your old pistons, put one old and one new piston in the cylinders and measure. Measure from BDC to the top of the cylinder deck on both cylinders. With a good steel ruler you should be easily be able to see if there is a significant difference. High tech measure, use a dial indicator.
On compression: you can run the motor on one cylinder with the gauge in the other cylinder and the motor will only develop x amount of compression. It does not matter if you have to pull the cord 100 times if it is still moving the needle on the gauge. No offense intended but if you gave your sled little girl compared to burly manly man pulls the manly pulls just get to the maximum faster with less pulls.
Just a side note. I have two compression gauges. Gauge one will demonstrate 90psi as a maximum in my motor. My second gauge (also bought from Autozone) will report 130psi in the very same motor. The compression number your gauge/motor reports should not be directly compared to your buddies gauge/motor. With your 90psi recorded in a note book and years from now is gauge checked again with 87psi then you have something. You can monitor your wear. Say in two years of racing your sled is becoming difficult to start and the compression is down to 80psi per cylinder. You can expect with re- chroming the cylinders, new pistions/rings to get back to 90psi.
Altitude can also play an effect on compression. My motors (@5280ft) run fine if they put out at least 90psi both cylinders within 5% and start great.
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Alright... so we finally got nice weather and were ready to figure out if our engine was going to start/run with 90psi compression. We hooked everything up, and disappointingly, after hitting the starter a few times, the starter turned the engine over, but it wouldn't fire at all. My buddy grabbed a can of carb cleaner, sprayed into the carbs, and after that, the engine immediately started up and the revs increased rapidly (idle speed screw was turned in 1.5 turns like the manual states). I had to back off the idle speed screw a good 3/4 turn to get it to idle around 2500rpm. We shut if off shortly after and when trying to start it again after about 5 minutes, it again wouldn't start. Again, a spray of carb cleaner got it to start right up. Choke didn't seem to have any effect one way or the other. I'll also mention it's about 65 degrees when we were doing this if that makes any difference.
Once we had the motor running for a while, we noticed something else. When restarting the motor shortly after it had been shut off, it would start up, idle low and rough and then die. I had to turn the idle speed screw back up that 3/4 turn, start it, and after a second, the revs would start climbing so I would back it off that 3/4 turn and have it idling at 2500 again after which it seemed to run ok.
Just trying to figure out what these might be symptoms of. We are running on 35:1 premix. The motor seems to run fine (though we haven't had a load on the engine yet as the clutch is off) but has trouble starting. Any ideas? Thanks!
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If you are running 35-1 oil plus the oil injection it might be to much?? It should smoke a lot. Do you know the condition of the fuel pump?
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Yes, it smokes like crazy. We bled the air in the oil lines so the oil injection is working full time now as well. Fuel pump is brand new. How much of a difference does it make that we don't have the clutch on as far as the idle speed screw is concerned?
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you don't think someone maybe opened up the cylinders a bit, might be keeping the rings from sealing all the way, or maybe cylinders are out of round?? never had a motor I rebuilt down around 90 psi after assembly.
90 PSI will be hard to start.
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Ok, understood. But will 90psi seemingly run ok without a load on it once it's started? Or would it run rough? Like I said, it starts right up with a little spray of carb cleaner. I am going to get a good compression gauge now because I don't know if I trust the readings off this old one.
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Just got home with the new compression tester and the results are gooood. 130psi in both cylinders =)
So this means our starting problems are not a result of low compression but rather something else... probably carb related. Any other ideas out there for why an LTD motor would not want to fire unless carb cleaner or something similar is used, but runs perfectly fine once it's started? Also, the idle speed screw needs to be turned in more to get it started, but then has to be backed out because the engine revs climb to around 4000rpm. Thanks!
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What carbs do you have on it? Did they get soaked in carb cleaner and all passages opened? Joel
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90psi, 130psi, why do I bother?
Replace the main jets, power jets, pilot jets and the rubber o-ring in the carburetor. Verify the pilot passage is clear. Balance the carburetors.
If there is still trouble fix the fuel pump. A new fuel filter (big automobile type), open the fuel pump and rebuild or inspect for serviceability and replace the impulse line.
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90psi, 130psi, why do I bother?
Replace the main jets, power jets, pilot jets and the rubber o-ring in the carburetor. Verify the pilot passage is clear. Balance the carburetors.
If there is still trouble fix the fuel pump. A new fuel filter (big automobile type), open the fuel pump and rebuild or inspect for serviceability and replace the impulse line.
Haha I just looked back and you really nailed those numbers, lol. Where is the best place to get replacement jets for these carbs? I have the Keihin BD40-36's on this motor. Thanks!
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Are you sure your compression tester is accurate?
Alot of guys pull the Keihns off and put on a set of Mikuni's. Parts for the Keihins can be hard to come by...
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The accelerator pump diaphrams are still available,however the bowl gaskets (orings) are difficult to find or not at all,but if you can keep it in tact and use anerobic gasket maker (Permatex) with the old gasket it works great. Jets can still be had as well. Joel
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i would say hard starting could be caused by the keihins,kinda touchy, [what idle screw do you speak of, speed or mixture?]also, put the clutch on, it also acts like a flywheel,adds to rotating mass at idle.
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Dump the Keihins and flush up some 36mm or 38mm Mikuni's. Likely all carburetors are good and good enough for the Kawasaki manufacturers of the sleds to call them OEM. This only applies when they are new and then only warranted for the year. Thirty years go by and guess who is my number one choice for even used old carburetors.
Claim away but do not ask me to help you start or tune your sled if you have other than Mikuni. My poor friends, belly up and admit what so many learn.
Follow through with purchasing 38mm and those specifications I can share. Better search the forum and find your answers.
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on my 82 ltd i used a set of 440 invader carbs and started rich,[many junked invaders]ended up at stock jetting,runs very nice,trucker even mentioned how well it started.[no e start]
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I have an extra set of 440 Invader carbs if you're interested, PM me.