Spark plus RV125L

[malky]

Hi guys - I have a 1973 RV125L with a single range transmission and noticed that the head has got holes for a long reach and a short reach plug - the question is which one do I use and what plugs are supposed to in there ? I guess one is for on road and one for off road but which is which ?
Mal.

[dorT500]

Hi guys - I have a 1973 RV125L with a single range transmission and noticed that the head has got holes for a long reach and a short reach plug - the question is which one do I use and what plugs are supposed to in there ? I guess one is for on road and one for off road but which is which ?
Mal.

I've never even been around one of those little guys but looks like fun....one hole is for a compression release kit or the factory block off plug.

Only install one spark plug....use the block off plug and it's gasket for the other hole. Plugging the hole with another spark plug can cause damage. It has to do with the increased heat generated by that extra spark plug...... even though the other plug is the only one lighting up.

It was explained a lot better than I just did and in more detail and to the satisfaction of many by a very trusted, knowledgeable professional vintage/modern motorcycle mechanic on another forum a few years back.


Looks like the head may have been superceded by another later but is this the fin arrangement on yours?







Another style head that may have been use later...







https://www.cmsnl.com/suzuki-rv125-1974 ... 1Ytkpe8qPs" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

[malky]

Yes mine is the later style in the picture so which plug should I be using - the short reach or the long reach? The left hole sitting on the bike is long and the right is short
Mal.

[dorT500]

Yes mine is the later style in the picture so which plug should I be using - the short reach or the long reach? The left hole sitting on the bike is long and the right is short
Mal.

Hello malky,

The deeper/tall hole is for the compression release if one wanted one and could find the correct one.





Just a generic example of a compression release..



I think I saw the spark plug would be an NGK brand B7HS (12.7 mm threadreach) You might want to confirm that yourself. I always use NGK brand but here is a cross reference for other brands.

http://www.sparkplug-crossreference.com ... GK_PN/B7HS" onclick="window.open(this.href);return false;"

The B7HS happens to be the spark plug for my T500 also. Just for heck of it, here are a few pics of one in a T500 head off of a salvage yard engine I bought years back.

[malky]

Thanks dorT500. I'll have to get a new blanking plug then- why would you need to fit a decompression valve to a 125cc two stroke though ? - there isn't that much compression to start with !
Mal.

[dorT500]

.......why would you need to fit a decompression valve to a 125cc two stroke though ? - there isn't that much compression to start with !
Mal.

For engine braking....I'll let Dan elaborate...... scroll down just a bit. http://www.dansmc.com/comp_release2.htm" onclick="window.open(this.href);return false;