717 engine reving high then dies

[langdonb]

I just took out my 1998 sportster with twin 717 engines. The starboard side sarted fine but after going 5-10 knots for several minutes the tach went way up to 6 then back down to normal, it eventually died and would not restart. It has rebuild carb, new spark plugs, new fuel pump and filter. I was told the electrial box was going bad could this be the issue?

thanks

[Technical Support]

Re: 717 engine reving high then dies

Do a compression check on the engine. If the compression is around 150 then pull the rotary valve cover off and make sure that the rotary valve is turning when you crank the engine over.

[langdonb]

Re: 717 engine reving high then dies

compression was checked about 1 month ago and was fine, so I will check the other. Would that keep it from starting?

[John Kubiak]

Re: 717 engine reving high then dies

Check the compression anyhow....One thing to always remember, it only takes a moment of improper running to completely destroy a two-stroke engine!

[langdonb]

Re: 717 engine reving high then dies

Oh that is just great. Assuming bad compression are we talking full rebuild? The engine is only about 1.5 yrs old.

[dsolie]

Re: 717 engine reving high then dies

No, but at least a top end.

[langdonb]

Re: 717 engine reving high then dies

thanks for the info. could the electrical box have anything to do with this? I know it is old and needs to be replaced.

[dsolie]

Re: 717 engine reving high then dies

Elec components have been known to cause a lot of strange symptoms in motors. The only two things that could be an issue in the elec box is the rectifier or the rev limiter. I would suggest doing the low cost / free checks (compression & rotary valve) before throwing $$ into elec parts.

[langdonb]

Re: 717 engine reving high then dies

Thanks for your help, I will let you know how it goes. I have a hunch it is the rectifier and/or maybe the rotary valve.

[langdonb]

Re: 717 engine reving high then dies

Just to clarify. Would a bad rectifier and/or rev limitor keep the engine from starting? It will turn but not start.

[dsolie]

Re: 717 engine reving high then dies

Rev limiter can, but not often. Have you verified spark? What's your voltage at the battery?

[langdonb]

Re: 717 engine reving high then dies

I have not checked volts but the port engine starts fine, so if it was the battery wouldn't it affect both? As a side note both electrical boxes got water in them in the fall, although dry now could it be slowly shorting out?

[dsolie]

Re: 717 engine reving high then dies

It could be a plethora of things. The main thing is to verify spark and fuel...

Edit ** - You really need to take a compression test still..

[harkisy09]

717 engine reving high then dies

The porting was different on the white engines, so if you jetted for it then it will probably be wrong for the silver engine. Im not sure on pickup locations...they did completely redesign the silver engines over the white though.

[John Kubiak]

Re: 717 engine reving high then dies

Please make sure your advice is accurate and relvant to the current subject!

You seem to have the 947/951 info confused with the 717.

Langdonb is referring to "port" as in port and starboard or left and right. The 717 engines did not change internal porting when they changed from white to silver... Some later models of the 717 had external differences, such as the mag housing and rear mount brackets that resulted in the elimination of the bed plate mounting assembly. There was a 717D engine (that was white) in 1997 that was only used in the SP (model 5879) with reduced port timing and a 132° Rotary Valve , but it was not a very popular model and was dropped quickly.