I have had my WR430 rebored and they have supplied a wossner 8051D050 piston, however it protrudes out of the barrel by approx 1.5cm any ideas

I searchedkymco spike 125 and found a number of possible hits very easily. Go to wemotor. com/bikes/kymco/spike 125.. This looks like a possible one.

replace piston and rings and gudgeon pin and bearing , check condition of con rod for wear also ! check bore for wear and if it can be rebored ! ?? it will fail and cause more damage !!!

Poor compression I expect. Fit new rings and rebore the barrell to bring the compression up again. Using easy start or eather will damage the piston and seats.

It seems you have worn rings and/or barrel and piston. You will have to get the barrel off the engine to ispect. Unbolt the carb and exhaust from the engine. Unbolt the 4 nuts on top of the head. Remove the head and barrel from the engine. Inspect the piston for scoring and wear. Remove the piston by removing the circlip next to the gudgeon pin. Do not drop the clip into the engine.(stuff some clean rags in the engine under the piston. The gudgeon pin can now be pushed out of the piston and the piston removed.Have the barrel and piston measured for wear.
If you're on a tight budget you can replace rings only but this is a penny wise pound foolish solution. You'll have the same problem in 2 months time.
It is best to rebore the barrel and fit an oversize piston and new rings. The barrel can also be resleeved but this is a more costly option and should only be exersized if you cannot obtain an oversize piston.

Yes, but be careful not to over do it as you need to have a matching oversise piston ring. Most you can re-bore is 2 times with 0.05mm oversize total. Good luck.

Hi,
Most late modle MX & enduro (from about 1990 on plus some even earlier)
have what is called an electrofusion bore.
This is a very thin plating on the alloy cylinder. They use this so as to allow heat to dissipate quicker & can run tighter piston cylinder tolerances for improved performance.
To answer your questions,
No, they can't be re-bored(like the older style steel sleeved bore bikes could)
Yes, they can be honed but it requires a special type of hone(finger type bottle brush style hone).
Pistons are available increasing in size by much smaller incriments than the old style & are usually marked A,B,C,D(as the coating is much thinner than steel sleeve).
If it is scored very badly & you can see alluminum spots/scores anywhere on the cylinder surface there are several ways to deal with this.
Here in Australia there is a company(electrocill) that can re-cote the cylinder which is much cheaper(plus thicker & stronger) than replacing the barrel
If you have a cylinder re-coated It has to have all studs, seals & power valve assemblys removed.
You would also need to supply(or have them supply) a new piston in order for them to set the correct clearance.
Also here in Australia you can have most of the common models fitted with a sleeve & this gives you the abillity to rebore in the future.
In the U.S this company is known as Wisco(serco in Aust.)
It is worthy of noting that the piston rings are not interchangable between an electrofusion & steel type cylinder.(so if you opt for a re-sleeveing any spare rings from your spares kit ar of no use).
If you need a lead on how & if these services are available in your country(if your not in Australia) I suggest taking a look in the classified section of your local dirt bike magazine.
The trick is to undertake regular srevicing of your air filter(this is A MUST),oiling it properly with propper foam filter oil, useing a top quality 2stroke oil(motul,syn-lube for eg)
& regularly inspect & replace rings/piston as needed to get the best life from electrofusion or steel type bores
Hope this explains it all for you
Regards Andrew Porrelli

buddy its not an easy job to do as if the barrel has been damaged that much it will have to rebored to an over size piston or a new sleeve installed or if its just a little scratch you can get some glass paper and run it around the barrel not stying in 1 place at the same time do this until smooth also you can take it to a shop and get them to rehone it for you or rebore it also when you put the new one in oil the rings and make sure the arrow is pointing towards the exhaust valve

Your barrel? LOL. Sounds like the valves need to be gone through. I would suggest taking and valve train apart and put it back together correctly then go from there.

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whats wrong with them??