What's caused this Damage?

Si · Post by Si » Sun Apr 03, 2011 9:13 pm

Firstly, I'd like to say a big hello to everyone. I've been watching for a long time, but this is my first post.

I've got two KR-1S a C2 and C3, which both have engine damage.
Engine One:

Engine Two

What are your thoughts on what caused the damage? Thanks, Si

buzinc · Post by **buzinc** » Sun Apr 03, 2011 10:26 pm

Hi.

Are these two separate engines out of two different bikes or is it a case of one engine failed in the bike, so you have swopped in a donor engine - and obtained a similar failure?
Only say that because it seems to be the r/h pot on both accounts!
The crankcase castings are fine, they have a steel insert where the bearings sit.

Buz

Si · Post by Si » Sun Apr 03, 2011 11:06 pm

Hi Buz, yeah the engines are from two separate bikes that I have. Thanks, Si

KR-1R · Post by **KR-1R** » Mon Apr 04, 2011 1:45 am

$0.02

both engines are using non-OEM pistons (Mitaka) - so have been rebuilt previously - so not all damage may relate to current blow-up

Engine 1:
gummed up/sticky rings - seizure from possibly too long between re-ringing. (some people can make engine last XX,000 some can blow up below 10,000). Varnished ring grooves:
Over a long period unburnt oil can build up so that rings bind (overcoming ring tension, or the ring wears outside operating limits) and no longer seal the piston/bore correctly.
This piston is realatively intact - could crankcase damage be from previous rebuild problem? this case damage is not attribuatble to the piston alone (check conrod Big End clearance)
- mileage of engine
- oil seal (gear box oil burnt on right piston?)
- quality of injector oil (as per above does other piston show any ring build up)
- loading/running engine below powerband for long periods

Engine 2:
orange electrode colouration (and the hole in the piston) means that cylinder suffered sufficiently weak and compressed fuel mixture at the edge allowing detonation and becoming extremely hot, melting and eroding.
- spark plug grade/sizing (temperature) - check centre electrode, plug gap
- ignition timing (other piston is very black too, carbon build up is also source of pre-ignition)
- detonation, insuffient squish clearance - check barrel's height against opposite cylinder measurement
- carburetor/fuel problem (lean, old/low octane)

General:
I hope you have engraved each set of crankcases - the halves of each crankcase are machined together as a set (including balancer cover) - they should not be interchanged. If you are not careful, you won't remember which upper half belongs to which lower. You could end up with bearing surfaces that are out of round.

Ancient Quizz:...
http://kr-1s.co.uk/forum/viewtopic.php?p=36961

alimorg wrote:...I have discovered the perfect sized 'bung' - virtual pint to the first person who can tell me what they are:

Cheers
AL

name that bung

Post by **alimorg** » Mon Apr 04, 2011 9:22 am

KR-1R wrote: Ancient Quizz:...
alimorg wrote:...I have discovered the perfect sized 'bung' - virtual pint to the first person who can tell me what they are:

Cheers
AL
name that bung

Ohh I know I know!

TwoStroke Institute · Post by **TwoStroke Institute** » Mon Apr 04, 2011 1:17 pm

No1
I would say the big end bearing has gone south and the piston has hit the head causing the rings to jam, it's obvoiusly got hot that caused the pick up. Original cuase lack of lubrication.

No2
Holed piston is sure sign of too much ignition advance. I would be checking crankpin phasing.

maccas · Post by **maccas** » Mon Apr 04, 2011 1:23 pm

Engine 1 looks to have tzr250 1kt pistons in so i would expect the barrels to have been bored out to fit them or a liner has been put in?

Standard bore tzr is 56.40mm and kr1s is 56mm?

Maccas

Si · Post by Si » Mon Apr 04, 2011 2:53 pm

Hi guys, I really appreciate your replies. A little background info on the two engines:

Engine 1 had a complete engine rebuild by Stan Stephens about 8 years ago including a stage 3 tune, which cost me an absolute fortune. The bike at the time had a full nut and bolt rebuild.
I ran the engine in, then shortly afterwards (few hundred miles) she went bang!! Because, I was unhappy with Stans work, I stupidly went to a local two stroke specialist (their words, not mine) who advised me the best thing to do was put in steel liners, which they did for me.

Shortly after getting the bike back on the road she went bang again.

Engine 1 is running the original oil pump and I've always used Rock Oil Synthesis 2.

The crank has also had the same treatment as 500Bernie "Bolt and Braces, Bodge" post.

The bike has not been used since.

Engine 2

I bought this C3 in red and silver (absolutely stunning) a couple of years ago off ebay. The chap I bought if off used it for track days; its running on premix and daytime MOT.
Last summer, after annihilating =D> a couple of mates on their Ducatis, she lost all power.

After losing a little faith in my two strokes I am now at the point where I am dying to get back on two wheels this year.

I'm not sure if it helps, but are the barrells in a different state of tune:

This is the first time I've done any engine work, so I'm not very technical. What are your thoughts on my best course of action with the engines. My plan is to get one bike back on the road for this summer, on a daytime MOT. The other bike i plan to do a full nut and bolt rebuild returning her to a fully standard condition (when time and funds permit). I have got spare barrels, head and crank.

Are those bungs the specialists ones you get from Unilever =D> ?

Post by **alimorg** » Mon Apr 04, 2011 5:15 pm

Si wrote:Are those bungs the specialists ones you get from Unilever =D> ?

Close, they are acually the caps off A crown match pot tester tube!

Cheers
AL

TwoStroke Institute · Post by **TwoStroke Institute** » Tue Apr 05, 2011 3:06 pm

Stan eh seems Stan's name and 'cost me a fortune' usualy end up in the same sentence.

I don't like iron liners in cylinders designed for Nicasil, some do OK but I have never found them to be reliable.

Your No2 fail is definatly ignition related.

KR-1R · Post by **KR-1R** » Tue Apr 05, 2011 9:42 pm

who wants to start a fan club?