Motorcyle Repair Recommendation

Major · 09-18-2014, 04:47 PM

I hate to give up a trade secret since he's so busy, but call Pete Dyer at Laconia Motorbike. 524-9275. Good luck.

Dave R · 09-18-2014, 08:56 PM

The backfiring upon shut down is normal for those. You can fix it with a carburetor re-jet. Since it's a simple, air cooled single-carb engine, it should not cost much at all to re-jet it. I have heard that it likes a #152 main, a #50 pilot and 1/4 turn out (from the stock setting) on the idle mixture screw. With these changes, it should make more and smoother power too. It will use a bit more gas though.

Slickcraft · 09-19-2014, 06:29 AM

Quote:

Originally Posted by Dave R

The backfiring upon shut down is normal for those. You can fix it with a carburetor re-jet. Since it's a simple, air cooled single-carb engine, it should not cost much at all to re-jet it. I have heard that it likes a #152 main, a #50 pilot and 1/4 turn out (from the stock setting) on the idle mixture screw. With these changes, it should make more and smoother power too. It will use a bit more gas though.

Cate, this does not sound any more difficult than the lawn mower carb that you rebuilt. Maybe you can find on line instructions and order the new jets along with a book on Zen.

Dave R · 09-19-2014, 09:17 AM

Changing jets on a Mikuni carb like the on that that 650 thumper is really easy. Also because the bike has so much open space under the carburetor, you don't even need to remove the carburetor to do it.

Here are two videos I found by googling "savage 650 jet change": https://www.youtube.com/watch?v=0j-nPtoP2MY and https://www.youtube.com/watch?v=qpHQk-pA6fI

You may be able to fix it with just jet changes (without adjusting the idle mixture, which involves the use of a drill, something that tends to scare people a bit when working on a carburetor...).

CateP · 09-19-2014, 09:56 AM

I don't think I'm going to attempt this re-jet project. BUT it's really good to know what's involved and why it's happening. Very informative group here.

I'm going to give Laconia guy a call.

Dave R · 09-19-2014, 11:16 AM

The jet recommendations I made assume the bike is stock. If it has been modified with an exhaust system or air cleaner change, it will likely require very different jets. Good luck.

PM me if you can't find a local mechanic to do the work, I'm just over an hour away via some sweet motorcycle roads (I know, a 2+ hour round trip is a really long ride on that bike...) and fully able to do the work. I only do this stuff as a hobby, but I have decades of experience on all kinds of bikes and can arrange to do it while you wait/watch or even teach you how, if you'd like.

dpg · 09-22-2014, 07:04 AM

I second letting it idle a little. Although totally unrelated my rider mower always back-fired if you turned the key off when the machine was in a low idle. Finaly after readibng through the owners manual (and someone telling me) I found out I had to keep the engine racing on high then turn the key to "off." Hasn't happened since in two seasons now.

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09-18-2014, 04:47 PM	#1
Major Senior Member Join Date: May 2013 Location: Laconia Posts: 1,109 Thanks: 451 Thanked 1,038 Times in 435 Posts	Laconia Motorbike I hate to give up a trade secret since he's so busy, but call Pete Dyer at Laconia Motorbike. 524-9275. Good luck.

09-18-2014, 08:56 PM	#2
Dave R Senior Member Join Date: Jul 2004 Posts: 2,985 Thanks: 246 Thanked 744 Times in 444 Posts	The backfiring upon shut down is normal for those. You can fix it with a carburetor re-jet. Since it's a simple, air cooled single-carb engine, it should not cost much at all to re-jet it. I have heard that it likes a #152 main, a #50 pilot and 1/4 turn out (from the stock setting) on the idle mixture screw. With these changes, it should make more and smoother power too. It will use a bit more gas though.

09-19-2014, 09:17 AM	#4
Dave R Senior Member Join Date: Jul 2004 Posts: 2,985 Thanks: 246 Thanked 744 Times in 444 Posts	Changing jets on a Mikuni carb like the on that that 650 thumper is really easy. Also because the bike has so much open space under the carburetor, you don't even need to remove the carburetor to do it. Here are two videos I found by googling "savage 650 jet change": https://www.youtube.com/watch?v=0j-nPtoP2MY and https://www.youtube.com/watch?v=qpHQk-pA6fI You may be able to fix it with just jet changes (without adjusting the idle mixture, which involves the use of a drill, something that tends to scare people a bit when working on a carburetor...).

The Following User Says Thank You to Dave R For This Useful Post:
CateP (09-19-2014)

09-19-2014, 09:56 AM	#5
CateP Senior Member Join Date: Jan 2011 Location: Wolfeboro Posts: 868 Thanks: 584 Thanked 540 Times in 210 Posts	I don't think I'm going to attempt this re-jet project. BUT it's really good to know what's involved and why it's happening. Very informative group here. I'm going to give Laconia guy a call.

09-19-2014, 11:16 AM	#6
Dave R Senior Member Join Date: Jul 2004 Posts: 2,985 Thanks: 246 Thanked 744 Times in 444 Posts	The jet recommendations I made assume the bike is stock. If it has been modified with an exhaust system or air cleaner change, it will likely require very different jets. Good luck. PM me if you can't find a local mechanic to do the work, I'm just over an hour away via some sweet motorcycle roads (I know, a 2+ hour round trip is a really long ride on that bike...) and fully able to do the work. I only do this stuff as a hobby, but I have decades of experience on all kinds of bikes and can arrange to do it while you wait/watch or even teach you how, if you'd like.

The Following 2 Users Say Thank You to Dave R For This Useful Post:
CateP (09-19-2014), Winnisquamguy (09-20-2014)

09-22-2014, 07:04 AM	#7
dpg Senior Member Join Date: Apr 2004 Posts: 2,624 Thanks: 157 Thanked 236 Times in 173 Posts	I second letting it idle a little. Although totally unrelated my rider mower always back-fired if you turned the key off when the machine was in a low idle. Finaly after readibng through the owners manual (and someone telling me) I found out I had to keep the engine racing on high then turn the key to "off." Hasn't happened since in two seasons now.