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oldoo
03-22-2018, 07:09 AM
Hi all,
So my 87 trx 70 doesn't like to run with the choke off. It will pop and bog... with quick acceleration, but with slower acceleration it isn't as bad but still not good. If I flick the choke up and it's fine and ridable compared to with choke off.

The carb has been cleaned out a couple times. Needle is set in the middle position. I havn't changed it around...
carb rebuild kits? Are the shindy ones any good? They're made in Japan but haven't found any good reviews.

The https://uploads.tapatalk-cdn.com/20180322/2e91e52d58bc6871cb1e550187318019.jpgoil has been changed, new air filter, new spark plug...

Any advice would be great.


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oldoo
03-22-2018, 07:16 AM
Also, I would buy a new carb to get the darn thing to run right. Can I run an atc 70 carb (I can buy one new) and change the jets??


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shortline10
03-22-2018, 08:06 AM
Is your air box fully connected with no leaks ?

Shawn Powell
03-22-2018, 03:35 PM
Start with just brand new jets. Sounds to me like I’d start with a new pilot jet. My xr400 did this when I bought it. Cleaned it. Same thing. New jets no problem. I think it had old fuel stuck in the jet. Like a barnie of sorts. Couple bucks and she isles and runs great.


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DAM shop
03-22-2018, 03:44 PM
Also, I would buy a new carb to get the darn thing to run right. Can I run an atc 70 carb (I can buy one new) and change the jets??


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I wouldnt buy the so called "new one" off Ebay those are aftermarket carb's and not all that reliable. Stick with your oem carb and check the things the others have mentioned..

oldoo
03-22-2018, 03:53 PM
I wouldnt buy the so called "new one" off Ebay those are aftermarket carb's and not all that reliable. Stick with your oem carb and check the things the others have mentioned..

The so called new one I would buy would be a new oem atc 70 carb then just put the 62 main in from a trx. That should work right?




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oldoo
03-22-2018, 03:55 PM
Start with just brand new jets. Sounds to me like I’d start with a new pilot jet. My xr400 did this when I bought it. Cleaned it. Same thing. New jets no problem. I think it had old fuel stuck in the jet. Like a barnie of sorts. Couple bucks and she isles and runs great.


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Thanks mate, worth a shot for sure. I think I should be checking for air leaks too


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efhondakid
03-22-2018, 10:32 PM
My honest opinion, carb rebuild kits are a sham. There is no real "wear" parts in them. Putting new jets in and it fixing the problem just means you didnt have the old ones clean. The pilot jet especially on the little horizontal Hondas are so small that even a small speck stuck in it will render it useless. Compressed air is the best way to get the crap out of them, just hold on to them cause when they shoot across the garage they are pretty hard to find hahah.

ironchop
03-22-2018, 10:43 PM
.... Putting new jets in and it fixing the problem just means you didnt have the old ones clean. ....

I agree with this statement 100%




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fieldy
03-22-2018, 10:50 PM
While back someone thought they had their carb clean. They ended up disassembling it again and said they boiled it in lemon juice and that cleaned the gunk that was petrified and fossilized in those passages. Before that he was certain it was clean. Cheap something to try!

ironchop
03-22-2018, 11:00 PM
... They ended up disassembling it again and said they boiled it in lemon juice....

This is what I do. My sister in law taught me this method and it works great and I only have to clean it once.

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fieldy
03-22-2018, 11:05 PM
@ Ironchop. Real lemons or the stuff in a plastic lemon, lol?

ironchop
03-22-2018, 11:13 PM
Real lemons or the stuff in a plastic lemon?Same brand as the plastic lemon stuff but in the big bottle...https://uploads.tapatalk-cdn.com/20180323/f0e7c126ff4a0980971b904717e88d41.jpg

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ironchop
03-22-2018, 11:22 PM
I use about 1/3 lemon juice and 2/3 water

If they're really gummy I add more lemon juice

Boil for 30 min

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oldoo
03-22-2018, 11:50 PM
Ok great. Thanks for the advice I'll try that.

Also the needle shows signs of wear/rub marks so an oem needle kit looks like Its on the cards


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ironchop
03-23-2018, 12:07 AM
Ok great. Thanks for the advice I'll try that.

Also the needle shows signs of wear/rub marks so an oem needle kit looks like Its on the cards


Sent from my iPhone using TapatalkThat's natural. The needle is a little loose in the slide so it contacts that emulsion tube it goes down inside to the needle jet below sometimes. If it's not deeply scratched, it should be ok.

Needle getting bent or the end dinged is why they usually get changed out or if you're picky about your fuel curve and a master carb tuner.

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oldoo
03-27-2018, 05:39 AM
That's natural. The needle is a little loose in the slide so it contacts that emulsion tube it goes down inside to the needle jet below sometimes. If it's not deeply scratched, it should be ok.

Needle getting bent or the end dinged is why they usually get changed out or if you're picky about your fuel curve and a master carb tuner.

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Ok cool. I got a nos needle jet kit but will only use it when absolutely necessary.

For those following. New jets have been ordered from partzilla and hopefully arrive in Aus this week. Will keep you all posted, fingers crossed the new jets get the old girl running as she should.


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oldoo
04-06-2018, 12:10 AM
So guys, I installed new jets.... still no luck. I'm leaning towards an air leak? Tried to diagnose it by spraying wd40 listening for a change in sound but no change in engine not I could detect.


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oldoo
04-06-2018, 09:29 AM
Update, I found an air leak in the boot that connects carb to air cleaner. On the air cleaner side. Will be ordering a reproduction boot from spanglers and hopefully that fixes it.


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shortline10
04-06-2018, 09:41 AM
That’s why I asked my question in post number 3 .
The air box needs to be 100% sealed or they run like your description .

Tomcall
06-08-2018, 05:09 PM
are you running with the original stock air box or an aftermarket air cleaner? Curious as I am having issues myself ever since I installed the hotter cam from dratv.

oldoo
06-10-2018, 03:10 AM
are you running with the original stock air box or an aftermarket air cleaner? Curious as I am having issues myself ever since I installed the hotter cam from dratv.

Yeah oem airbox and brand new filter. I am yet to fix the air leak as I have been busy attacking the rear end. I'm sorry but I don't have much experience with the hot cams in these motors so can't really help you.


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