the motor's out & cracked open...

[sleddineinar]

I've cracked open my crankcase to replace the outer crank bearing that was bad. when I had the motor sitting so I could see the pistons through the exhaust ports I noticed that my middle piston is very scored, the other 2 look OK to me, a little scoring can be seen through the exhaust port. I took the head off and can see that the cylinder wall on the exhaust side of the center cyl. is worn as well. I've never had a hi-perf 2 stoke apart before, so I'm a novice with anything more than chainsaws and old lawnmowers. I was just wondering why that center would score more than the others. I'm assuming that I should replace that piston and put new rings in all three. I'll check the cyls and oterh 2 pistons to see if they are in spec. I might add that I did a compression test before taking it apart and got 122/125/125 readings.

 

[sideshowBob]

We would need pictures to give you any kind of accurate assessment of the centre cylinder/pistonr damage, but here is some possible causes:
-dirty carbs[centre worse then others]
-jetting changed from the stock settings ending up too lean on centre cylinder
-overheating
-carb iciing
-air leak around reed cage and/or carb flange
-too hot of spark plug...stay with stock plugs

Red Heads are darn reliable and if they are stock they don't need high octane fuel, 87 is fine. If the sled is piped or has higher compression you will need premium fuel...just like SRXs and bad fuel can cause problems that lead to the scoring

JM.02c

 

[sleddineinar]

Sorry for not posting pics last night, but I was at work... and sorry for the crappy pictures I'm posting right now, but I'll have the cylinders off tomorrow maybe and then I'll take better pictures. These are just of the center with the head off and through the exhaust port. To me the top looks really rich that's why I'm puzzled by the scoring, but I'm leaning toward old damage by the previous owner. This motor has always been a bit heavy on oil consumption.

 

[sideshowBob]

IMO:

That cylinder has been running rich + that actually does not look that bad...I don't see any metal transfer from the piston to the cylinder. The engine could have got hot at one time or more or it may have been riden hard before a proper warm up, or its just high mileage wear + tear.
I would ball hone that cylinder[I know I'll get grief over ball honing]If you can't catch your finger nail on any of the vertical marks in the cylinder, put a new set of pistons + rings in it, make sure the jetting is safe, clean the carbs and you should be good to go.

JM.02c

 

[sleddineinar]

Thanks Bob. I'll post pictures of the other two pistons and cyls, but what I was most surprised by was what looked to me like a big difference in the scoring on that piston and the others. The other 2 have a small score mark on each of them, while that one has got a lot more. I was wondering why one would show more wear like that. Anyway the cyl. walls don't have scores that you can actually feel, so what you are suggesting is kinda what I was thinking, replacing the piston or pistons if they are all of spec and putting new rings in it, and seeing if it will hone at all, I know those cyl walls are pretty hard...

 

[sleddineinar]

Oh BTW, I don't know how much difference it would make, but when I last rode this sled, the skid collapsed on it and I rode it out of the woods at just over engagement rpms for about 45 minutes. I was wondering if the pistons would wash that much in that time, I have the fuel screws set to 1.75 turns out. The pilots are stock but the needles are dropped a 1/2 clip and the mains are 142 across. When you see the other pics the PTO cyl. is washed even more. It was around 20°F that night.

 

[sideshowBob]

The jettting you are running is leaner then stock.[ 1-145.0, 2/3 143.8]...I would most likely go back to stock mains + needles at least for the break in of the rebuild. The leanest I would set the needles on an SX700 would be position 3 with both plastic washers on top of the clip, but I would caution that leaning any sled today from stock settings is risky as our fuel quality has declined dramatically over the last few years.
There is no money to be saved by running cheap oil either, put the best quality oil in your oil tank you can get!
Another interesting item is that the only piston we ever scored on our piped, ported SX700 was the centre cylinder...since then I run all the cylinders jetting as rich as the PTO...same all across.

 

[Mitchell49601]

U people scare me !

Cheap, I've been told U can hone a cast cylinder, But when it comes to a nikki it's not so simple as told to me by Pat Hauke, He always does my nikki cylinders as far as guessing who's the best at doing motor work, Who on this site actually has a buisnees and has raced at pats level, I'm not trying to sponser hauke or anything , But when U talk to him on the phone he'll set U straight, No one on this site has whipped him, I think not

 

[Mitchell49601]

Won't last !

With todays exspectations from a sled (Shade tree will not cut it) Hauke for a minimal cost will do a wet hone and they will check your cylinder walls in 3 places just like what should be done, Low,Mid ,High, Priceless to tell U it's good, No dought about it.

 

[sideshowBob]

LMAO!...You scare easy!
I knew as soon as I mentioned "Ball Honing" the action would start! LOL!

-First off...NO ONE is questioning Hauck Power Sports credentials or reputation, they speak for themselves..how Pat got invoved with this discusion is an inigma???

-secondly...Nikasil cylinders are so hard that a conventional hone will not remove any of the coating, usually only specialized shops have the proper equipment to actually hone material away.

-third...A properly sized ball hone will not remove material from a Nikasil cylinder but it will clean + deglaze the surface so it can be better inspected for damage. The danger of using a Ball Hone is that during use the balls could hook a port or fragile skirt of the cylinder and damage the actual cylinder.

People have been using Ball Hones for deglazing and cleaning up cylinders[including Porsche 911 similarily coated cylinders] for a long time...not all people would agree but when used properly + cautiously it is NOT SHADE TREE MECHANICS.

JM.02c

 

[middlman]

I will add that when I bought my sxr and went to put pipes on noticed it was scratched on intake and exhaust side with scratches in the nicasil wall plus transfered aluminum. We took it down, new pistons and rings.. used myriatic acid to eat the aluminum off the cyl walls (it fizzles white) (sp) then used a 120 grit ball hone to break any glazing etc.. I have 1100 trouble free miles this yr, it is runnning perfect and starts well and runns fast and uses around 260 miles per oil fill. Just make sure you can't hang a nail on the scratches of the wall and you are good.

you can get good jugs for 130-150 each.. less than recoating. Then I'll buy your scratched jugs because I want a set to resleeve and turn into a 750

 

[midwestoffroad]

i have had my share of burn downs and have always acid the alum out of the cylinder and used a ball hone to clean them up. and have used sandpaper (emery cloth) on the suborn alum pieces. nicacil is pretty tuff

 

[YAMAHIZAL700]

Cheap, I've been told U can hone a cast cylinder, But when it comes to a nikki it's not so simple as told to me by Pat Hauke, He always does my nikki cylinders as far as guessing who's the best at doing motor work, Who on this site actually has a buisnees and has raced at pats level, I'm not trying to sponser hauke or anything , But when U talk to him on the phone he'll set U straight, No one on this site has whipped him, I think not

Not really sure what horse this guy rode in on but it sure sounds like to me that you have no ability to work on motors since you endorse pat hauck so much. From what I read bob has a wealth of knowledge and he didnt get it sittin on the phone with hauck being set straight. So as for runnin off at the mouth and discrediting others helpful advice just keep it to yourself!

 

[Mitchell49601]

Sorry !

Not really sure what horse this guy rode in on but it sure sounds like to me that you have no ability to work on motors since you endorse pat hauck so much. From what I read bob has a wealth of knowledge and he didnt get it sittin on the phone with hauck being set straight. So as for runnin off at the mouth and discrediting others helpful advice just keep it to yourself!

I didn't mean to offend anybody, Alls I really ment was some of us don't have tons of $ to try and see if something will work or not, In my case I need to know without a dought it's fine, So I disagree on regular ball honing, I'm not the best and U aren't either, There is aways a better way to do something for sure, If (U) beleive there is only one way to do it and it can never be perfected then I feel sorry for U, And I'm sure theres alot of other people who are in the same shape, I've had great luck having Hauck prepare and inspect my engine parts for me before (I) put it together, sideshowbob does know and has given great input no dought U have not, Might want to make damm sure U have (No) Leakage in motor Seals #1) and make sure when U get it back going carb area is sealed, U leaned it up too much I hope, U can get it back going like or better than new, I just beleive in having a shop like hauke do my preliminary inspect,cleaning, They will tell U everything to make sure U are not putting half assed junk back together hope this clears things up, U will get it right, Again Sorry.