My kango 637 makes quite a lot of noise but lacks punch. In fact I get more out of a cheap breaker. Could this be a piston problem and where can I get spare parts from

kango 950 was the hammer drill version. Usually when they stopped hammering they were due for a rebuild. These units have a aluminum piston that rides in a steel tube striker. When the 2 rubber piston rings wear out you will get the described problem. The Kango's use a special tan grease so you cannot just yank it apart and replace the 2 rings with o-rings and grease. I had to rebuild 15 900 and 950's because the previous mechanic used the wrong grease. https://project21designs.com/kango-950-parts
The link sells grease & rings.

It is very likely the carbon brushes that contact the motor to transfer electricity to the windings. those tend to crack and get stuck or wear out. They need to be moving in and out freely and have spring pressure pushing them in towards the motor. you can get new ones cheap at ereplacementparts.com if they sell them.

Unfortunately Kango is out of business, they were a great hammer though. My understanding is Milwaukee bought them and marketed them mostly in the UK - you can still find some parts overseas but it is hit or miss.

Its the ask if its a MILWAUKEE kango 900K yes but if its a KANGO 900K the metal red or metal blue demolitionhammers its difficult to find but the cause of the broken con rod when the machine is not good air tight it can have has burned o-rings and more also the battle cilinder can be torned and piston pin not smooth enough and ,more parts of the original English KANGO are not simply deliverable anymore, but for the American milwaukee red 900k its not a problem
http://services.milwaukeetool.nl/jsp/material.jsp#part0239

For parts this old, I start out looking on ebay by the part number and brand. If that falls through, I look for the whole product on ebay because there might be one cheap enough to strip a part from. Fact is, I don't find the part elsewhere on the web, even in part replacement sites. You might contact customer service at Kango or Milwaukee Tools but such is a long shot. Here is what ebay offers: kango 750 rotary hammer: Search Result ' eBay

Hi Vicki
Is it the old all silver one or the new one with the red motor housing?

If these are the original Kango kangos then you are out of luck. They have been obsolete for many years now and no parts have been manufactured for a long time. The name was bought by DeWalt and they didn't do much with it. The Kango name is now ownd and used by Milwaukee, but there machines do differ alot from the originals. There were a few main models and the main mid sized breakers were the 900 (hammer only) and 950 (rotary hammer) There were a few facelift/variations of each (K, X and B I think) and they did use a couple of different sized seals/pistons/cylinders.
If it is one of the Milwaukee models you can look up diagrams here...
http://www.milwaukeetool.com/

There are a couple of main things that could cause this. Unfortunately this is an obsolete machine and I doubt you will be able to find any spares for it. Probable causes are worn seals/in need of service. Worn armature pinion gear and/or crank pinion gear. Ideally you should replace both if either one is damaged, even if the other one looks ok. There are always other possibilities but they it would need stripping on the hammer mech to check all the piston/pins/anvils etc. This is a very old machine (I cut my teeth on these when i started in the trade 20yrs ago).

Blue smoke is a direct indication your burning oil.This is a old truck and im assuming it has lots of milage.If this true either your valve seals are bad or piston rings are bad.Both of these cause oil burning,which will cause blue smoke and poor performance.

What kango hammer do you have? I am most familiar with the UK kango 900 and 950, pre-milwaukee.