800 Engine Issue - Connecting Rod

bchita

bchita

Member
Well, I got to rip apart my 800 to find the connecting rod has left the crank. Now I am looking for some pointers. Here is some info to assess and what I know to date.

1) Plugs 1 and 2, starting clutch side, look great, plug 3 solid black, and plug 4 almost look like it burnt down.

2) Engine just came to a nice gradually stop when I was slowing down, nothing loud or any indication of what I have now.

3) Airbox cone does have a tab missing on number 3 as well as some others.

4) No indication of tab in crankcase, just needle bearing and molten metal.

5) When purchased, Owner indicated top speed of 93, when I tried I got only 80. Not sure if this is relavent in this but everything I know. Put 101 miles on the sled since I bought it. Ran steady throughout.

6) Have done visual inspection and no indication of from oil pump not functioning. Will take fuel pump apart. I believe the oil mixes in the fuel pump?

Questions;

1) Oil Pump Issue?
2) Fuel Pump issue, not mixing correctly?
3) Electrical Issue?
4) Timing Issue, cranks

Any direction greatly appreciated !

Will replace right crank and cylinder, piston etc....
 

I recomend if your going to rebuild do it all. spend the money and you wont be disapointed. Thats what i did and i put 1000 + miles one it this season problem free. Once the engin is 100% move on to carbs and clutchs leave no bolt untuched put everything back to OEM SPEC then mod if you want to. You have all summer now, would be a good project. Do that and the only time you'll see 80 is when your letin your buddys catch up.
 
My 95 st did 106 GPS on hard packed trail/road. Sled all stock other than M-10 skid, spring and helix. NO BS 106 GPS..
 
Which cylinder has the bad rod? Which cylinder/cylinders have tabs missing?

I have had two 750's with busted/bent/effed up (bad) cylinders that I am near positive was due to ingesting a tab. There were no signs of the missing tabs on either but with the damage that was done it I did not expect a oiece of plastic to survive the calamity. So just because you can't find plastic in your bad cylinder doesn't mean it wasn't the culprit.

opsled

opsled
 
Cylinder 3 from clutch side has bad rod, and cylinder 1, 3, 4 have missing tabs, and 2 is almost cracked off, needless to say they are all gone now. I have enclosed pic of rod. Well anyone reading this post, remove these things!!! Not sure if it will affect performance from a hp standpoint, but in the long run, I think its worth it. Like to hear more from others, does this rod look similar to anyone else? There is still some rod stuck to the crank.

Rod.jpg
 
I wouldn't atribute that to an air box tab. My experiance with waht I thought to be an ingested tab was a completely destroyed piston (in pieces) and a rod that was broke/bent because it had nothing to keep it centered it the cylinder anymore.

You have a mostly entact piston and a wreaked lower rod bearing (big time). I think something else caouse your delema.

How is the upper rod bearing?? It appears to be OK in comparison to the lower.

opsled
 
To add. If you have a rod bearing going south your port timing will be way off and squish/compression will be down. A black oily plug would make sense in that situation.

opsled
 
Wrist pin bearing is ok, has some pieces stuck, but functional. Ok, this is good, so rule out tab, and looking at wrist pin bearing, good shape, would possibly lead to not a oil problem, rather a breakdown of the roller bearing, from something coming through the carb or just fatigue. The cylinder does not show signs of oil not being pressent, just the pieces that broke loose. Would like to see what others have to say.
 
I have now taken alook at all the cylinders and the crank is out. Below is a statement taken from vmaxmike and his crank episode. If the below statement is correct, cause I don't know, then I am out 45 degrees.

1 and 4 should be at tdc at same time 2 and 3 will be at tdc at same time this is how 4 cylinder inlines run.

Can someone verify the above statement to be correct, probably is, just want to make sure. Hypothetical, maybe way out there, because the sled would only do 78-80, could the crank come out of time so bad that number 3 cylinder be under so much stress and cause the crank bearing to go? Keep in mind the sled did not come to a grinding halt or a sudden jar. I stopped to cross an intersection at idle and it the engine just stopped really easy.

Any input greatly appreciated.
 
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Not sure where that quote came from but that would be a 180* engine. The correct check would be then #1 is at TDC then #'s 3 & 4 are at mid stroke in the cylinder (one going up & one going down).

In a 90* engine no two are at the top at the same time. example #1 TDC , #2 BDC, #3 & #4 mid stroke

When Pete was doing my crank (750) he showed me how to visually check alignment. The 750 gear has a second dot on it that is to be 45* off from the rod pin, not sure if the 800 crank is the same way.


M
 
I started this two hrs ago and just got back so you got some new info,I know on twins they do set timing out a little and port the engine accordingly gain alot of HP,I have noticed some of the race water cross sleds run hard and strong and then die in the water when they got hot,when taken apart the crank did move out was of balance causing the problem.
HERE'S MY TWO CENTS
1) you never know what the previous owner did or sometimes they don't know either or what damage they caused or don't even know the right stuff to do with a SM.

2) Any new sled you PU its worth spending some time from the get go checking all fluids,correct plugs, color,compression,spark,look into the cyl's and heads,check clean or replace all the filters,air box's, (especially with the 4 carbs need to pull the carbs and check,clean and set them and look at all the stuff under them like fuel/oil line pumps,oil leaks etc. Then do the other suspension,track,bolts,ski stuff.

3) #3 rod looks like lack of lube or lack of maint before you got.
4) #4 sounds like the carb was not working right lean,dirty or an air leak and ready to burn thru the piston.
4A) there's a plastic plate behind the carb "could be an insulator not sure" that Roadrunner told me to ckeck good known to crack and suck air.

5) only did 80 MPH something was wrong probably the carbs dirty from the get go.

6) plastic tabs missing you think you would see some damage to top of pistons or heads but would notice missing tabs in the pre inspection.

7) not sure what role the reed valves played out here.

7) previous owner could have mixed oils and sometimes don't mix well and cause big engine problems,never fogged engine end of season could have caused corrosion or the storage he had or poor maint.

8) you could add alota stuff to this list, I know hindsight is great and I don't always do what I say but do the pre check out on any new sled you PU is worth it and sounds like a lot of work but maybe 8 hrs and you know what ya got on the vmax4.

( now saying all this the last 96/800 vmax4 I got guy said was not run in two years,I said OK will check it out first do not try and run it,well I show up to look and they had it running but only run on half choke we shut it down and i did buy the sled,think it was shut down more like 6+ years when he got his new R1 1000 .
It took me about 13 hrs to pull and clean the carbs and reinstall "that bad",the 4 main jets were pluged and only two pilot jets open,so if I tried to run that sled half choke pulling gas thru the prime lines would have caused some serious damage to the engine.)

Hope some of this is constructive to you,but when you are convinced you know the problem please let us know.
 
Brian, anymore detective work on this?

It still troubles me as to what caused this. How much oil did it consume in the 100 miles?

M
 
The piston and rod look the one I took out of a Phazer about 10 years ago. Phazers are known for the floats needles seeping. Had a long trailer ride pulled it off and forgot to crank it over with the key off. It back fired and it was running like a champ, till about 60 miles into the ride mw wife slowed down to stop for a road and the engine just stoped. At that point you could only rock crank back and fourth about 3/4s of a turn. She said it was a bit down on power about 10 miles into the ride but not that bad that she thought it was a big deal. I figure it bent the rod on tha back fire and timming was not right, after a while the rod just snaped and the crank spinning did the rest of the damage. That one looks almost just like it, I had it hanging in the shop for years and just tossed it a few months ago.
 
Still would be interesting to know how much oil was used to solve this puzzle unless something else was found.?
 
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