real nice info here......but the whole idea of putting a wire in the hole is that engine is getting more fuel and less air......and to correct this we had reduced the petrol flow.........can't we simply set it for more leaner mix.....without changing the jet or putting a copper wire..........simply set the carb to leaner mix................guys wht do u think....

yes its possible, but requires some skill which the local mechs don't have. easy way out to put wire. better be safe than sorry principle.

simple solution

Rather making chnages and playing with the carborator, what i did was pretty simple - just take out the outer cover of the air filter, and you are back with all the power. Don't worry there is no way the dust can enter into the engine, and yes when you are back on the normal roads put the air filter back into it's positoin.

A smaller jet is THE right solution but getting one is next to impossible. HH don't keep such stuff with them and the thread profile of other makes do not match. So for the time being, putting a wire through the jet to reduce fuel flow is the only viable and available option in and around Leh.

You can only 'tune' for lesser fuel flow from the main jet by changing the jet with a smaller one. True, some changes can be made by lowering the needle position in the throttle slide but the ZMA default setting is already low enough. Going just a step lower makes no big difference. The 'tuning' you are referring to apparently is the air-screw adjustment found on carbs. The air-screw primarily adjusts the idling mixture and has no effect beyond 1/4 throttle operation. And idling is not the real issue with the ZMA at high altitude.

Just removing the air-box cover makes next to nil difference to the air/fuel ratio richness in the ZMA. Even entirely removing the air filter from the intake makes only a small difference. The ZMA engine runs very rich at high altitudes, especially above 14,000ft. And the only way of getting the air/fuel ratio to workable levels is by reducing the fuel flow vis-a-vis a smaller main jet or a wore through the existing jet.

By far the best solution .. rather than the wire alternative!!


True!! This 'air-screw-tuning' is of NO help! All the problems still remain..believe me..I tried every possible thing with that turning the screw and nothing helped..

A small correction here, the removal of the air-filter does help in getting back the power as while climbing Chang-La(17,000 + ft.) I had removed the air-filter and the bike was running absolutely fine with no issues at all. However, on getting back to Leh fitted back the air-filter and put a copper wire in the main-jet!

Here my friend you are wrong though about the technical aspect you are spot on.

Mikuni makes the carburettors for almost all indian bikes and also all indian cars as well and the jets are interchangeable and fit perfectly. I have run a maruti 800 mainjet in my pulsar 150 and the threads are a perfect match.

even the esteem, zen, contessa, ambassador 1.8, 118 ne, pretty much all cars that have ever had a carburettor post 90's have had only mikunis.

So the jets are very much available you just didnt look in the right place. even when i went to bike spare parts shop they had no jets , but going to a car spare parts dealer solved that.

Hello Sir, AFAIK many people use the ZMA jets to upjet the "Unicorn" which has 115 size jet. So I think the Unicorn jet should also be straight fit on the ZMA. Is there any chances that it won't fit in?

What a cheap and well-thought alternative, just the type of ingenuity you need to keep going... Brilliant, thanks for sharing that info

I wouldn't mind being wrong a thousand times over if there's something to learn involved . And inputs like yours here are what we are looking for. Since this is a thread related specifically to ZMA and ZMA-R 'Altitude issues', it would be great if you could give specific inputs about parts from which carb can be used on the ZMA carb to alleviate this mixture enrichment issue. There usually are innumerable examples of parts commonality amongst machinery but reinventing the wheel wouldn't be wise if someone like you has already done it.

And yes, by and by the ZMA comes with a Kehlin CV carburetor and getting parts support for kehlin's in India has been a pain all along. Mikuni and Kehlin jets are quite different and their flow characteristics do not go well with Kehlin carbs apart from differences in thread pitch. The Mikuni's even come marked differently, their round head jets being marked according to the hole size in microns and the hexagon heads being stamped with flow/unit time. The Pulsars, Bullets, Marutis and NE's all have Mikuni's and so interchangeability is possible. Like I said, please let the forum know which jet from what carb can be a direct fit for the ZMA here.

Shreeni: if people use ZMA jets on the Unicorn, then there's no reason why they shouldn't fit the other way round. Again, sourcing carburettor parts for kehlin carbs is a real pain. Ask those who've tried upjetting the ZMA. But the 115 from the unicorn should sort out the problem as the ZMA comes with a 125 main as stock.

Yes uni's jet 115 is a direct fit onto zma and will take care of running rich in higher altitudes. Should be easily available over the counter at honda A.S.S. If I recollect it right achiever is 119 which will be better as running 115 on highways might overheat the engine and will also dent the top whack and in gear pulling.


cheers
vishwas

Re: ZMA Higher Altitude Issue - Solution

Sorry if my opinion is wrong, but can we just turn off fuel valve on tank a little to limit the fuel goes into carb, will it make any juggad for getting lean mixer?

Re: ZMA Higher Altitude Issue - Solution

It will not as you are reducing the rate of fuel flow into the carb bowl from tank, not the rate of flow into the engine from carb

Re: ZMA Higher Altitude Issue - Solution

+100
There is a reason float bowl is provided as it acts as an fuel reservoir One more hack for this problem if you don't want to do wire thingy is to use unicorn's jet , it is 115 compared to 125 in ZMA and 128 in Xtreme.

Re: ZMA Higher Altitude Issue - Solution

Do we have any online source where one can get exact match of the jets wanted? Because, its troublesome to look for in near by garages..