unusual button found

[zad0107]

Hi to all and happy christmas.

I have just bought a nice drz 400 sm that appears to have an extra button ?? to the stock bike.

basically its mounted on a block next to the starter switch. the block has a couple of little holes in it. there is also a piece of clear tubing that is threaded through and under the tank. this tube goes into the carb i think also on a block..

Is this a hot start>>> it makes a small hiss when pressed..

this being the case. How and when are you supposed to use it ??

Edited December 20, 2009 by zad0107

[jones-moto-east]

a pic would be nice.

[bink98xcab]

hard to say w no pics. but it may be a kill switch attempt by PO that was never finished

[motothump]

it turns on your nitrous ,so hang on when you hit it!

[zad0107]

if i could work out how to post pics on here without them having to be on a web site i would put em on..

[mweitz]

if i could work out how to post pics on here without them having to be on a web site i would put em on..

Set up an account at photobucket. Upload the pic there then link to it here.

[zad0107]

here are the pics of the button... take a look and tell me what you think it might be.. please see the original post for description and question..

regards daz

[zad0107]

done that .. take a look im sure its not a standard button lol

[zad0107]

it seems to let air into the carb which makes me think its a hot start button

[mweitz]

what happens when you press it while it is running?

[zad0107]

there is a very quiet hiss of air sound from the holes on the button and the engine revs pick up very slightly hardly noticable though

[mweitz]

In my limited experience, you get a pretty big RPM increase with a hot start button...

Certainly strange.

Can't ask the last owner?

[forester801]

It reminds me of a priming bulb from lawn mowers. Maybe when you pump the button it pumps air into the vacuum petcock and lets the carb prime with fuel?

Thats the only thing I can think of.

EDIT: Just realized that his petcock is not a vacuum.

[zad0107]

this button does seem to suck air in rather than blow air out, the bike has no other mods that i can see at all.. still on stock can etc.. and only has 1,800 miles on the clock.. cant find anything else like it on any british sites either ? its a well made piece of kit though the button and inlet block are annodized and also the carb connector. this makes me think it is something designed and made for this or other trail / sm bikes

[zad0107]

Had a closer look at the button. And where it mounts into the carb...

I have confirmed that it is a hot start button. when i started the bike today i ran it up uo temp pressed it and the engine revs did increase. Spoke to a local specialist who confirmed that with the air tube being mounted under the choke letting more air in will have this effect. They do a similar mod to some of their bikes but with the use of a cable and lever or button on the carb.

[Erik Marquez]

Yes it is a hot start, no it is not really needed, but as it's there.. Keep it.

Though with the kink in the air tube

It is not doing much in any case.. Fix this issues or remove the whole thing to clean up the bars and remove a possible air leak..

[zad0107]

just had a reply from a british forum. Here is a link to the exact same button being sold in the uk.

http://www.racespec.co.uk/cgi-bin/sh000001.pl?REFPAGE=http%3a%2f%2fwww%2eracespec%2eco%2euk%2facatalog%2fPirelli%2ehtml&WD=start%20hot&PN=copy_of_copy_of_copy_of_Misc%2ehtml%23a48_2d9000#a48_2d9000

[zad0107]

Now that i have established that this button is a hot start button... not usually needed on base model sm... i investigated my carb a little closer and i have now found that on the side in big shiny letters it says KEIHN.. does this mean that my little sm is not quite as standard as i thought.. how do i identify the Keihn carb further without stripping bits off the bike. Are there any further id nos on the carb that sould be visible to identify it.. i will post a pic of the carb for you guys to take a peek at.

[ptgarcia]

Probably have an FCR carb on there. The SM came stock with a Mikuni carb.

[lento]

Yes it is a hot start, no it is not really needed, but as it's there.. Keep it.

Though with the kink in the air tube

It is not doing much in any case.. Fix this issues or remove the whole thing to clean up the bars and remove a possible air leak..

on that note, any ideas on replacing the petcock rubber ring ...:excuseme:mine is bad and dont want to buy the whole petcock assy...