This thing is driving me INSANE. I'm $2k into the engine and it still wont run right. Head rebuilt w/ new valves, guides, etc. Distro refurbed. Carb cleaned, adjusted ad infintium, and now a china carb thrown on it since the throttle and choke shafts were worn to leaky on the original. The exact same issues persist. The idle RPM is highly unstable, at seemingly random. This morning it refused to drop under 3krpm even once fully warmed up. This afternoon it idled right where it should right off the bat. Some days, it bogs when I tap the throttle or give it a little pedal before beginning to engage the clutch, frequently resulting in a stall. When *lightly* tapping the throttle, the RPM will drop a couple hundred RPM then bounce up before settling back to idle. It does it sometimes when it's cold, sometimes it persists even when it's hot. Sometimes it doesnt do it at all. I cant figure a rhyme or reason to it. When cold, when I get the thing rolling without stalling, it'll pull with some authority, then suddenly it'll lose half or more of it's power, at anything from 1/3 to WOT. Backing off the throttle, it'll suddenly snap back to running right... if I ease back into the throttle, it'll pull harder and harder then WHAM, suddenly loses a lot of it's power. The engine tone changes when this happens, but it doesnt sound like a classic misfire, more like random rapid sputtering. Once its fully warmed this tends to stop happening. I've timed it by the book, distro is on the right port, i've gone through the ENTIRE vac system and rebuilt it with color coded silicone tubing. I dont get it. Some days it runs almost right, some days it's just absolute undrivable garbage. *post edit: it should be noted the previous owner and the mechanics that rebuilt the head BUTCHERED the vac system... I dont know that I have the proper one way valves and restrictors and whatnot on it or in the right places. They seem hard to find and even the expensive translated manuals are no help with these.
Pulled the plugs last night for a sanity check. #1 looks a bit rich maybe? Verified timing is still dead on 7* at 950rpm. Verified functionality of the vac advance with a hand pump and the ported vacuum behaving as it should. Choke at least seems to be doing as it should. It still wants to stumble under moderate or more load when not fully warmed up, even in ~80 degree or higher temps. It still stumbles briefly upon blipping the throttle. I read somewhere the accelerator pump on these shouldnt be adjusted at all? Anyone mess with that? PXL_20240924_233049345 by dalez0r posted Sep 25, 2024 at 10:59 AM
There is no accelerator pump on the OEM carb for the Suzuki's and I think the Scrums are basically a badge engineered Suzuki Every from Mazda. Sounds like your choke is acting strange. When first fired up the choke may engage for a short time (higher idle etc) but in warm weather it should drop back down fairly quickly. I would recheck all the vac goodies, especially the one way jets (as they call them) that control things.
It is effectively a Suzuki Every van. Those arent accelerator pumps on the bottom with the little lever run into them? High idle works, the thermal pusher moves it off as it warms, and the F pod pulls choke off a bit immediately after starting if it's cold and fully closed. Once it's fully warmed the high idle drops to base idle... unless it doesnt.
Everything checked out (again). The only thing I noticed that may be off, when I clamp the PCV hose, the idle SIGNIFICANTLY drops. Like 500-600RPM. The PCV valve is "new", as in ~4 years and a couple thousand miles on it at most. And it probably wasnt OEM. Is it normal for THAT much flow through the PCV? It has a VERY slight rattle when I shake it.
Well I found one problem. The shop I had rebuild and reinstall the head didnt adjust the valve lash worth !@#$. The intake valves are at least .1mm too loose, and the exhaust are loosely flopping around much worse than that. They told me they adjusted it twice and it was just noisey
You're right, it did!! Much quieter now, I only hear one valve ticking just a little at idle now. Didnt have too much trouble hitting 65mph, although I'm a lot more comfortable with it at 50-55mph based on sound and the RPM it's turning. It still does this "bah-VROOM" when you blip the throttle sometimes, but it doesnt want to STALL when it does it now. Will get back to yall if it still acts up when cold after I let it cool overnight. Still cant believe a shop that bills itself as the best CUSTOM car shop in the county, that works on all kinds of hotrods and other rides, does full frame up builds, etc, can eff up valve lash THAT bad.
If it can get up to 65 then you are doing fine. They probably did the adjustment wrong or hot either way could result in loose floppy valves. Good to hear you sorted it out.
