Hornet 250 Wont Start When Engine Is Hot

[sira]

Dear Friends
My hornet 250 is 98. it starts morning without any issue. with 1,2 sec it start. after riding it for a hour and stop the engine, it dose not start quickly like morning. I have cleaned the carburetor change the air filter (not genuine) , change the Engine oil.

How ever the battery is not very good. plugs are looks very old but no any miss fire and light grey tip.

I'm trying to figure out the issue of this?

please advice

sira

[Watchman]

Do you know if it is overheating?

[The Don]

Two other possibilities

1. Fuel pump issues, air in the fuel line, or air getting into the fuel line due to a faulty clip

2. Engine is under compression so while its warm the piston gap is too great to provide enough compression for ignition.....

So you can confirm there is spark? Have you checked if there is fuel? I assume the bike has a mechanical fuel pump. Does it have a hand pump as well?

[sira]

Two other possibilities

1. Fuel pump issues, air in the fuel line, or air getting into the fuel line due to a faulty clip

2. Engine is under compression so while its warm the piston gap is too great to provide enough compression for ignition.....

So you can confirm there is spark? Have you checked if there is fuel? I assume the bike has a mechanical fuel pump. Does it have a hand pump as well?

Thanks Don

this dose not have any fuel pump. this is Honda hornet 250 and 4 carbs

[peugeot407]

Might caused by increased plug clearance with heat or HV leakage. Initially try replacing the plugs although it might be expensive since Hornet originally came with Iridium spark plugs.

[The Don]

Might caused by increased plug clearance with heat or HV leakage. Initially try replacing the plugs although it might be expensive since Hornet originally came with Iridium spark plugs.

Well he can test each plug by keeping it out and cranking. He should see a good spark.

I kind of think it could be the carbs. All the vaccume lines ok?

[sira]

Well he can test each plug by keeping it out and cranking. He should see a good spark.

I kind of think it could be the carbs. All the vaccume lines ok?

yes. seems ok. I have cleaned them first place with abro carb cleaner. did not dismantle whole cab as the plugs colour is light grey. no black smoke, and water on the exhaust in the morning.

[The Don]

yes. seems ok. I have cleaned them first place with abro carb cleaner. did not dismantle whole cab as the plugs colour is light grey. no black smoke, and water on the exhaust in the morning.

So is fuel drawn to the car with aid of gravity and suction created by the pistons during cranking? Sorry, my knowledge in bike engines are limited but I assume a lot of concepts from car engines are transferable.

If there is spark, reasonable compression, by a balance of probabilities once can asume its fuel delivery.

I asume yours is not a version which is ECU controlled?

[nsiva]

I also own one of the latest chassis of this hornet. It doesn't have a fuel pump. But has 4 carburettors. There is no ECU, but a CDI (ignition) unit with lot of pin outs. I have found that when I pull the choke even slightly the bike doesn't start.

Possible reason I can think for your hit start issues are,

1. Bad spark plugs, bad plug cars (rubber), bad coils. Actually if the ignition (high voltage wires) are old they might have more resistance. It can increase with higher resistance resulting in weak spark.

2. Bad starter solenoid or poor connections between battery.

3. Turn on your headlight & if possible measure the battery voltage with a multimeter. If it is below 12V surely it is the battery.

Remove the battery connections , clean & re tighten.

4. In newer models, the fuel tap is opened by vacuum line. Due to hot condition, if the vacuum leaks - you fuel flow may not be enough. I don't know whether your fuel tap is manual.

5. You may have a leak in (broken rubber parts) between carburettor and engine. This can cause air going from outside

Don't test the spark plug by removing the he wire leads without properly attaching an earth or test plug. I busted my ignition coil unnecessarily in my civic car...!

Start from simple like battery!

[Rumesh88]

yes. seems ok. I have cleaned them first place with abro carb cleaner. did not dismantle whole cab as the plugs colour is light grey. no black smoke, and water on the exhaust in the morning.

Things you have described above would not guarantee a properly adjusted carb set up in a Hornet/Jade. Also I do not think the use of carb cleaner is a good idea to clean this type of carb without dismantling it. When you dismantle the carb you can take out the rubber diaphragms first to prevent them coming into contact with the carb cleaner. There are several things that can go wrong with this type of carbs. Two basic things are the mixture screw adjustment and synchronizing adjustment in each of the four carbs. When these two are out it is a real PITA to get them right even with vacuum gauges on each carb. Also keep in mind that the carb needles of this model are known to wear out fairly quickly. I believe your frame is 105 and you have the same carb set up as a Jade. Do you have a electrically operated vacuum switch connected to the four vacuum lines from each carb like in a Jade?

[sira]

Thanks Rumesh

This is 115 chassis and no electrical vacuum . do you know any one do this all above sync and all in Colombo area?

[Rumesh88]

Thanks Rumesh

This is 115 chassis and no electrical vacuum . do you know any one do this all above sync and all in Colombo area?

I meant 115 but typed as 105. You can get this done by Chaminda of J*stin Mtors, Maradana. I do not have the contact number now but will send you a PM as soon as I find it.

[sira]

^{thanks guys , but this quickly start with push start? why it is easy. if the all carb issue, plug issue.......etc it should not start with push start too(I guess) ? any idea?}

Edited April 21, 2015 by sira

[sira]

Finally

1. Changed the battery

2. Changed the spark Plugs

3. Tune up the carb

Looks all fine and engine is very smooth. how ever the mechanic said the number 4 carb got a big than others and it is dark than other plugs .

any idea?.

Edited May 5, 2015 by sira

[Rumesh88]

If the carbs are synchronized properly all the cylinders should ideally get the same amount of air and fuel at any given throttle position. But in practice it is difficult to achieve this in a used carb because the needles and the seats could be worn out.

[sira]

Rumesh

Is there different jet size on number 1 cylinder Carb and rest. initially I got 90 on the number 1 carb (where the break paddle side - right to left 1,2,3,4) and others are 88. the mechanic now changed it in to number 3 as the vacuum pipe attached to fuel tap.

is this correct? or Number 1 cylinder must have 90 jet ?

sira

[Rumesh88]

Since the carbs are gravity fed they do not get an equal amount of fuel due to frictional losses in the fuel feed. This is compensated by having a slight difference in jet size for the carb/carbs located further away from the fuel tap. Thus you should have a larger jet size for No. 1 carb. (I rang up another friend to re-confirm the jet size but he did not answer. However as I remember 90 for 1st carb is correct).

[sira]

Thanks Rumesh

How about the other carbs are they 88 ? it is very small letters on the jet it may be 98 (not sure)

[Rumesh88]

Thanks Rumesh

How about the other carbs are they 88 ? it is very small letters on the jet it may be 98 (not sure)

All I know is that the jets are different by a very small amount. It should be 90 and 88 but not 98 I believe, and also more than one carb jet is different from the others (but I could be wrong here). In fact I do not have a similar bike or the repair manual at hand to check. However, if I get some more information from my friend I will keep posted.

[sira]

Thank you Rumesh

I found some thing related to this . it says the Jet, Needle jet and camber set float are different in carb number 4. see this post http://www.hondahornet.org.uk/messageboard/viewtopic.php?f=53&t=29616.

What is camber set . float?

i think i need to find more details on this . now 1,2 plugs are bit a dark, but 3, 4 are perfectly white.

need to find a guy with more specific with CBR and Hornet. found few chaps and they are telling 10 different stories on this.

[Hoonigan]

If you've narrowed it down to the carbs, it would be better to have them looked at by a specialist I think. I used to get the carbs on my Bandit tuned by someone near Piliyandala with excellent results. You might know that the bandit carbs are notoriously troublesome compared to Hornets. If you live nearby I can PM you the details.

[sira]

Thank you and please PM the contact

[Rumesh88]

Thank you Rumesh

I found some thing related to this . it says the Jet, Needle jet and camber set float are different in carb number 4. see this post http://www.hondahornet.org.uk/messageboard/viewtopic.php?f=53&t=29616.

What is camber set . float?

i think i need to find more details on this . now 1,2 plugs are bit a dark, but 3, 4 are perfectly white.

need to find a guy with more specific with CBR and Hornet. found few chaps and they are telling 10 different stories on this.

What you mean is Chamber Set, Float I guess. That is the float and other related accessory set for the carb.

BTW if your cylinders 1 and 2 are a bit dark compared to other two then either there is a problem with synchronizing the throttle plates or the needles are worn out or bent thus producing erratic fuel flow at different engine loads. Even if you sync the carbs perfectly at idle it may not be the case at higher loads. Does any of the mechanics you tried use a vacuum gauge set (that's a set of four gauges in fact) when tuning the carbs or do they just listen to the engine beat and do it?

[sira]

Yes,

they do listen and tune. the mechanic called Chula at arangaala. he looks ok and did not have vacume

[Rumesh88]

Yes,

they do listen and tune. the mechanic called Chula at arangaala. he looks ok and did not have vacume

That's what they normally do but not a very precise method. The four carbs are totally independent except for the throttle linkage. Each throttle plate can be adjusted individually but the linkage is interdependent. Knowing how difficult to sync the carbs even with four vacuum gauges and a color tune kit, I just can't imagine how one is able to adjust the carbs by listening to the engine beat. Did you try Chaminda @ J*stin Motors?