Suzuki DT40 2strk...Backfire...

[oceanview]

Hello All,

I have a '89 DT40 2strk; it was parked up for a while in a w/house;
sold as it was supposedly siezed. Motor was not siezed; turns quite
nice. Took out plugs; misted cylinder and turned by hand; then used
started; motor turns nicely; lots of puffing and comp feel good.

Cleaned fuel filter; checked fuel pump (it's pumping); so all up to that
point seems good; spark at plugs; disconnected oil monitor guage as
it seemed not even want to fire up.

The engine will not fire up; appears that plug on cyl1 are dry; plug 2
(bottom) is wet; when it does want to fire; it backfires thru the prop/cav plate area.

I need some help as follows;

1/ what could be causing the backfire?
2/ should I remove card and clean throughly?
3/ what do I look for with reed valve?

Can someone point in which direction I should be troublshooting?

Thanks much,

m...

[noelm007]

If you have spark, then a carb rebuild is in order, they need to be stripped and cleaned properly, not just sprayed with something, reeds give very little trouble as a general rule, however a "proper" backfire can damage them, more than likey a good carby clean will see it running again, have you done a compression test? if not, do one now.

[oceanview]

dt 240

Thank you for your reply. I have been thinking that I should strip them down, I just was hoping I didn't have to; but my gut feeling was telling me I should; and now you too...funny. I'm just a little nervous about stripping down the carb and getting the linkages set back correctly.

Compression was bumping up, but I suspect the rings may be a little stuck; and I really don't want to take it down that far; so I'm hoping there is something I can do to help with the rings.

Anything else you can offer advice wise is apprecaited.

Regards,

[boats.net]

Throughly clean carburetors, do an accurate compression test, anything above 100psi should run the engine. If still no success, check timing.

[Max_SA]

Rough Running

I also have an approx '87 DT-40 with similar problems to Oceanview's.

I have used the engine a few times (3 or 4) and it went relatively OK at full throttle, though it's no Rolls Royce. It idles very rough (and once backfired on starting when cleaning with muffs). I've changed the plugs and still the same. Today, I started it on the water, putted around with slightly higher idle and choke out. Put the choke in and then the engine revved up, then down then up then down (without me changing the throttle) and then lost power and cut out.

Would not start after that. I'm not sure whether this is a carb issue (flooding perhaps) or whether there is something else wrong? The previous owner did mention that the float occasionally gets stuck. Is there a way that I could find out if it is worthwhile to overhaul the carb or whether the engine is poked? How easy is it to disassemble the carb and put in new jets/float etc? I see that Brownspoint sells spares and carb kits. (Suzuki DT 40c (1986-1998) Fig. 4 - Carburetor)

[oceanview]

DT40 2 stoke...

Since post above; I put project on hold as other stuff came up. I'm now ready to start again; and was wondering if someone could help with some info.

If I turn flywheel and get the piston to TDC; can someone tell me what the timing degree line on the flywheel should be pointing to/at; and if I need to move the throttle lever say half way; what other mark/position should I look for by flywheel and spark advance mechanism.

Of course I'm trying to get away from a strip down..smile..so I want to ensure all other things should be where they need to be. The carb was stripped; cleaned and put back; fuel pump is working; getting spark to plugs; and it cranks. The symptoms are wants to fire; sometimes backfires through prop; honestly can't recall if through the carb as well.

Doing a compression test; it's jumping between 85 /90/ 100..so I'm hoping its
just sticky rings.

The only other thing I may need is which wires go where (connection); info for the oil gauge; or how to bypass it temporarily; as I'm not sure about that.

Thanks...

[oceanview]

DT40 2 stoke...

Hey Max SA, were you ever able to get your problem resolved? If so, what was the solution.

Thanks..