Jetting Hitachi Carb at altitude - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 08-06-2007, 08:34 AM
geckocycles
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Jetting Hitachi Carb at altitude

I just got a 88.5 Sammi. 1300 cc

It has only 38000 on it with 31's and a Calmini 3" spring under lift kit. I had to remove the ft. bumper and mounts. It is a one owner and was owned by an old couple who towed it behind the RV. It is such an awesome rig. Looks like new except for some stitching rot on the rear seat.

Anyway I live in Denver area and go up to 10000' or higher. It runs very rich all the time and secondary operation is useless. I did 100 miles full throttle going to Neb. and it got 14 mpg. No power at all. Gets 23 mpg on primary cruising at 55 mph. I believe it has stock gearing so that is the next project. Going with a transfer case gear swap from Spidertrax who are 15 miles away from me.

Smells like rotten eggs and rich condition.

I had no exploded view of parts breakdown for this at the time I took the top off. I did now find one on Autozone.com. I think there are some hidden jets under jets that I didn't see until I got the exploded view.

Has Hitachi carb. I took the top off and wrote down all the jets that I could see including the mains. Not sure what I'm looking at though.
One in the middle and the two on the sides of the ports. 3 jets in the top, 70 secondary side, 140 primary side and 65 middle.
3 on the top of the base. 70 secondary, 100 primary and 60 middle.
Mains are 85 primary and 140 secondary.
Starts fine when cold and slow to start when hot. It has a rich start when hot.

I would like to keep this carb for now. It is like new but a bit confusing with all the electrics and vacuum lines. I will replace it later for more power, but I'm up for the challenge first. I don't believe this has been driven hardly at all. The miles on it are mostly tow miles. Not rust spot on it except minor discoloration under bra.

Are these stock jets? It seams a bit off to me. I was a tune-up tech in my youth but not on this carb. I had many VW bugs, some with dual Webers for the drags and most with Zenith carbs for my baja's. What I'm saying is that I'm familiar with fiddling to make things work.

Can you give me a jet configuration for this altitude?
I know I should go FI with these altitude changes being so extreme. Is there a kit for that swap so I can research that option?

Thanks so much for any help.
KB
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Last edited by geckocycles; 08-06-2007 at 08:37 AM.
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post #2 of (permalink) Old 08-11-2007, 11:20 PM
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If you are running that rich you have a problem. (As if you didn't know) I am not that familiar with a stock carb model, but I thought that there are many others that have extensive knowledge of the workings of carbs and their spec's on here and am surprised they have not chimed in. Anyway I did look in my book and it says;
"High altitude compensation is used for compensation of air/fuel mixture(and idle speed). Fuel compensation is accomplished by mixture control solenoid supplying additional air to control air passages. High altitude requirements are determined by control unit based on signals from high altitude compensation switch. At elevations lower than 4000 feet switch is open and voltage is high, at over 4000 feet switch is closed and monitored voltage is low."

So it would seem that the system is self-compensating and if not, there is a problem with the compensation system. You should download a copy of the FSM as at Ack's FAQ: Suzuki Sidekick and Geo Tracker 4X4 offroading information. It may have the #'s for the stock jets but in my book it sounds like they don't use them. It should give you the procedure to check the system and find out the problem. Many things control this and it will give you a checking procedure to isolate the problem.
If you change it to Fuel Injection I can be of more help. Good luck!
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