Motorcyle Repair Recommendation

[CateP]

Hi there. We are looking for a motorcycle repair person in the Lakes Region (close to Wolfeboro if possible) who can fix a backfiring situation. The bike is a 2008 Suzuki Boulevard S40. The owner is a teacher without a lot of extra $$ to spend.

Recommendations most appreciated.

[beaner]

I recommend getting a good pair of ear plugs. :laugh:

[Dave R]

Does it happen under heavy load, under steady light load, or is it just when letting off the throttle? If it's only when letting off the throttle, that's common on those and an easy fix. The idle mixture is set very lean to pass emissions and it can be richened up a little bit to cure the popping.

[CateP]

Backfire happens when she turns off the engine. Sounds as loud as a gun shot and startles everyone...including the pups.

[Woodsy]

Sounds to me like it might be carburetor related.... I would run some carb cleaner thru the tank. Also, only use premium fuel.

If that doesn't fix it, a tune up probably will.

Woodsy

[Rusty]

Let it idle for @20-30 sec's before turning it off and see if it still does it.

What cause backfiring is usually excess fuel that still wants to burn and causes vapor lock which in turn causes it to backfire.

This should not happen so it does need to be fixed.

Sorry I don't know of any Motorcycle Repair Businesses.

[HomeWood]

Might be a carb issue. That backfire sounds like gas fumes igniting in the exhaust. My commercial mower does it if I shut it off during higher rpms. The motor is still sucking gas in as it cranks down (with no spark) and sending raw fuel/fumes into the hot exhaust. Then boom!

It could also be gas igniting in the combustion chamber when the key is turned off. Same thing as exhaust, it's still hot enough in there to ignite the gas.

Tune up, cleaned carb, and running higher octane gas may very well solve this.

[Major]

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]

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]

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.:rolleye2:

[Dave R]

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]

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. :cool:

I'm going to give Laconia guy a call.

[Dave R]

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]

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.

[dpg]

Might be a carb issue. That backfire sounds like gas fumes igniting in the exhaust. My commercial mower does it if I shut it off during higher rpms. The motor is still sucking gas in as it cranks down (with no spark) and sending raw fuel/fumes into the hot exhaust. Then boom!

It could also be gas igniting in the combustion chamber when the key is turned off. Same thing as exhaust, it's still hot enough in there to ignite the gas.

Tune up, cleaned carb, and running higher octane gas may very well solve this.

Funny as I've posted my STOPPED back firing when shut down during high RPMs?? :confused:

[SAB1]

I ride an '05 boulevard S83. Before you bring it anywhere run down to NAPA in back bay and buy a can of Seafoam. Fill the tank and add Seafoam as directed. I would use in a couple tanks before I brought it to be serviced. I had same problem and Seafoam fixed it. I run a round of Seafoam through every fifth tank or so.

[CateP]

I ride an '05 boulevard S83. Before you bring it anywhere run down to NAPA in back bay and buy a can of Seafoam. Fill the tank and add Seafoam as directed. I would use in a couple tanks before I brought it to be serviced. I had same problem and Seafoam fixed it. I run a round of Seafoam through every fifth tank or so.

Well that's just great because I happen to have a stash of Seafoam that I got when it was on sale. Love the stuff for all our small engines.
Great advice and thanks!!!

[HomeWood]

Funny as I've posted my STOPPED back firing when shut down during high RPMs?? :confused:

Machines can be so unpredictable and two of the same may act totally different but that is odd. :confused:

Seafoam is good stuff. Worth a try and might as well throw a new plug(s) in it since they're cheap enough.